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moved defn of RTS_SUPPORTS_THREADS from Rts.h to Stg.h

Remove mention of PrimOpHelpers.h.

--------------------------------------------
        Translate out PrimOps at the AbstractC level
        --------------------------------------------

This is the first in what might be a series of changes intended
to make GHC less dependent on its C back end.  The main change is
to translate PrimOps into vanilla abstract C inside the compiler,
rather than having to duplicate that work in each code generation
route.  The main changes are:

* A new type, MachOp, in compiler/absCSyn/MachOp.hs.  A MachOp
  is a primitive operation which we can reasonably expect the
  native code generators to implement.  The set is quite small
  and unlikely to change much, if at all.

* Translations from PrimOps to MachOps, at the end of
  absCSyn/AbsCUtils.  This should perhaps be moved to a different
  module, but it is hard to see how to do this without creating
  a circular dep between it and AbsCUtils.

* The x86 insn selector has been updated to track these changes.  The
  sparc insn selector remains to be done.

As a result of this, it is possible to compile much more code via the
NCG than before.  Almost all the Prelude can be compiled with it.
Currently it does not know how to do 64-bit code generation.  Once
this is fixed, the entire Prelude should be compilable that way.

I also took the opportunity to clean up the NCG infrastructure.
The old Stix data type has been split into StixStmt (statements)
and StixExpr (now denoting values only).  This removes a class
of impossible constructions and clarifies the NCG.

Still to do, in no particular order:

* String and literal lifting, currently done in the NCG at the top
  of nativeGen/MachCode, should be done in the AbstractC flattener,
  for the benefit of all targets.

* Further cleaning up of Stix assignments.

* Remove word-size dependency from Abstract C.  (should be easy).

* Translate out MagicIds in the AbsC -> Stix translation, not
  in the Stix constant folder. (!)

Testsuite failures caused by this:

* memo001 - fails (segfaults) for some unknown reason now.
* arith003 - wrong answer in gcdInt boundary cases.
* arith011 - wrong answer for shifts >= word size.
* cg044 - wrong answer for some FP boundary cases.

These should be fixed, but I don't think they are mission-critical for
anyone.

Profiling cleanup.

This commit eliminates some duplication in the various heap profiling
subsystems, and generally centralises much of the machinery.  The key
concept is the separation of a heap *census* (which is now done in one
place only instead of three) from the calculation of retainer sets.
Previously the retainer profiling code also did a heap census on the
fly, and lag-drag-void profiling had its own census machinery.

Value-adds:

   - you can now restrict a heap profile to certain retainer sets,
     but still display by cost centre (or type, or closure or
     whatever).

   - I've added an option to restrict the maximum retainer set size
     (+RTS -R<size>, defaulting to 8).

   - I've cleaned up the heap profiling options at the request of
     Simon PJ.  See the help text for details.  The new scheme
     is backwards compatible with the old.

   - I've removed some odd bits of LDV or retainer profiling-specific
     code from various parts of the system.

   - the time taken doing heap censuses (and retainer set calculation)
     is now accurately reported by the RTS when you say +RTS -Sstderr.

Still to come:

   - restricting a profile to a particular biography
     (lag/drag/void/use).  This requires keeping old heap censuses
     around, but the infrastructure is now in place to do this.

extend the scope of the doNothing() macro; can now be used in Stg headers

Retainer Profiling / Lag-drag-void profiling.

This is mostly work by Sungwoo Park, who spent a summer internship at
MSR Cambridge this year implementing these two types of heap profiling
in GHC.

Relative to Sungwoo's original work, I've made some improvements to
the code:

   - it's now possible to apply constraints to retainer and LDV profiles
     in the same way as we do for other types of heap profile (eg.
     +RTS -hc{foo,bar} -hR -RTS gives you a retainer profiling considering
     only closures with cost centres 'foo' and 'bar').

   - the heap-profile timer implementation is cleaned up.

   - heap profiling no longer has to be run in a two-space heap.

   - general cleanup of the code and application of the SDM C coding
     style guidelines.

Profiling will be a little slower and require more space than before,
mainly because closures have an extra header word to support either
retainer profiling or LDV profiling (you can't do both at the same
time).

We've used the new profiling tools on GHC itself, with moderate
success.  Fixes for some space leaks in GHC to follow...

Move extern declaration for 'environ' from Stg.h into HsPosix.h

Remove annoying warnings about using a deprecated extension
when compiling via gcc-3.0.

#if __GNUC__ >= 3
/* Assume that a flexible array member at the end of a struct
 * can be defined thus: T arr[]; */
#define FLEXIBLE_ARRAY
#else
/* Assume that it must be defined thus: T arr[0]; */
#define FLEXIBLE_ARRAY 0
#endif

A test program (hsking) compiled fine with gcc-3.0!

Change the story about POSIX headers in C compilation.

Until now, all C code in the RTS and library cbits has by default been
compiled with settings for POSIXness enabled, that is:
   #define _POSIX_SOURCE   1
   #define _POSIX_C_SOURCE 199309L
   #define _ISOC9X_SOURCE
If you wanted to negate this, you'd have to define NON_POSIX_SOURCE
before including headers.

This scheme has some bad effects:

* It means that ccall-unfoldings exported via interfaces from a
  module compiled with -DNON_POSIX_SOURCE may not compile when
  imported into a module which does not -DNON_POSIX_SOURCE.

* It overlaps with the feature tests we do with autoconf.

* It seems to have caused borkage in the Solaris builds for some
  considerable period of time.

The New Way is:

* The default changes to not-being-in-Posix mode.

* If you want to force a C file into Posix mode, #include as
  the **first** include the new file ghc/includes/PosixSource.h.
  Most of the RTS C sources have this include now.

* NON_POSIX_SOURCE is almost totally expunged.  Unfortunately
  we have to retain some vestiges of it in ghc/compiler so that
  modules compiled via C on Solaris using older compilers don't
  break.

Apply stat fix for mingw. It's ugly, it's implausible, but it seems to work.
Unlike Cygwin...(missing no. 3).

Remove all vestiges of INTERPRETER and __HUGS__.

merge recent changes from before-ghci-branch onto the HEAD

Clean ups:

   - reduce the namespace pollution of StgTypes.h, it doesn't define
     the shorthand versions any more (W_, I_ etc.).  These are moved into
     Stg.h.  StgTypes.h also defines StgClosure as an "opaque" struct.

   - RtsAPI.h is now standalone, and includes HsFFI.h and thereby
     config.h & StgTypes.h.  Now we don't need to #include "Stg.h" in
     *_stub.c.

   - all the rts_mkXXXX and rts_getXXXX functions are defined in terms
     of the HsXXXX types rather than random C types (this fixes some
     potential bugs in our foreign export support).

   - added HsWord type, to match StgWord.  The Haskell version of this
     type isn't "documented", but perhaps it should be.

Bug or feature? Changed `envyron' back to `environ', otherwise
hslibs/posix/cbits/env.c can't be compiled. If this breaks something
on M$, it must be #ifdef-ed somehow, but not simply be renamed.

Changes to allow Hugs to be built with mingw32, not cygwin.  Also,
updates so that DietHEP works properly for mingw32.  Most changes are
trivial (assert --> ASSERT), etc.  For hugs, have deleted queries
about the width of a terminal window, and so the printing of dots
as progress indicators is gone too.  No great loss.  Zapped various
other out-of-date platform-specific junk in machdep.c.

Make stackOverflow prototype available Haskell compilation

Change NO_MACHREGS back to NO_REGS -- I misunderstood the problem.

back off from _POSIX_C_SOURCE=199506L to 199309L, because the former
causes a bunch of extra functions thread-related to be compiled into
each module on Solaris.

#define _POSIX_C_SOURCE 199506L
#define _ISOC9X_SOURCE

Changed NO_REGS to NO_MACHREGS to avoid inexplicable gcc warnings when
building the rts for Hugs.

misc profiling cleanups

Simplified prog_* externs a little

Move Prelude.h from ghc/includes into ghc/rts.  It's essentially a
list of the things from the Prelude that the RTS depends on, and isn't
relevant to STG code.  Furthermore, this helps to clarify which parts
of the RTS depend on things from the Prelude (by an explicity
#include).

Merged GUM-4-04 branch into the main trunk. In particular merged GUM and
SMP code. Most of the GranSim code in GUM-4-04 still has to be carried over.

Fix up some problems with the IN_STG_CODE macro.

A slew of SMP-related changes.

 - New locking scheme for thunks: we now check whether the thunk
   being entered is in our private allocation area, and if so
   we don't lock it.  Well, that's the upshot.  In practice it's
   a lot more fiddly than that.

 - I/O blocking is handled a bit more sanely now (but still not
   properly, methinks)

 - deadlock detection is back

 - remove old pre-SMP scheduler code

 - revamp the timing code.  We actually get reasonable-looking
   timing info for SMP programs now.

 - fix a bug in the garbage collector to do with IND_OLDGENs appearing
   on the mutable list of the old generation.

 - move BDescr() function from rts/BlockAlloc.h to includes/Block.h.

 - move struct generation and struct step into includes/StgStorage.h (sigh)

 - add UPD_IND_NOLOCK for updating with an indirection where locking
   the black hole is not required.

_ccall_GC wibbles

This commit adds in the current state of our SMP support.  Notably,
this allows the new way 's' to be built, providing support for running
multiple Haskell threads simultaneously on top of any pthreads
implementation, the idea being to take advantage of commodity SMP
boxes.

Don't expect to get much of a speedup yet; due to the excessive
locking required to synchronise access to mutable heap objects, you'll
see a slowdown in most cases, even on a UP machine.  The best I've
seen is a 1.6-1.7 speedup on an example that did no locking (two
optimised nfibs in parallel).

	- new RTS -N flag specifies how many pthreads to start.

	- new driver -smp flag, tells the driver to use way 's'.

	- new compiler -fsmp option (not for user comsumption)
	  tells the compiler not to generate direct jumps to
	  thunk entry code.

	- largely rewritten scheduler

	- _ccall_GC is now done by handing back a "token" to the
	  RTS before executing the ccall; it should now be possible
	  to execute blocking ccalls in the current thread while
	  allowing the RTS to continue running Haskell threads as
	  normal.

	- you can only call thread-safe C libraries from a way 's'
	  build, of course.

Pthread support is still incomplete, and weird things (including
deadlocks) are likely to happen.

Redo previous commit to cut down on the use of COMPILING_RTS where
possible - SchedAPI.h is now an RTS internal header file which
RtsAPI.h no longer includes.

Don't include RtsAPI.h when compiling RTS.

Stg.h contains all the defs and protos that are visible when compiling
.hc code (==> .hs code). Augment this set with the externally visible
RTS API.

Comment about TABLES_NEXT_TO_CODE.

New define: TABLES_NEXT_TO_CODE says whether info tables are assumed
to reside just before the code for a function.   We used to use
USE_MINIINTERPRETER for this function, but it makes sense in certain
cases to separate the use of tail-calls from tables-next-to-code.

StgMacros: add a couple of missing macros to support update in place.

(this is number 8 of 9 commits to be applied together)

  The CPP flag LAZY_BLACKHOLING has been moved up from options.h into
  Stg.h, so GHC can see it as well as the interpreter, and
  EAGER_BLACKHOLING has been added.  The default is still
  LAZY_BLACKHOLING && !EAGER_BLACKHOLING.

Added a DllMain() which starts up RTS upon DLL load.

Moved DLL-related macros out of Stg.h and into separate .h file

Remove flags field from info tables; create a separate table of flags
indexed by the closure type in the RTS.

DLL_IMPORT_DATA_VAR fix

- misc changes to support DLLs
- StgNat* --> StgWord*

Copyright police.