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This is patch that adds support for interruptible FFI calls in the form
of a new foreign import keyword 'interruptible', which can be used
instead of 'safe' or 'unsafe'.  Interruptible FFI calls act like safe
FFI calls, except that the worker thread they run on may be interrupted.

Internally, it replaces BlockedOnCCall_NoUnblockEx with
BlockedOnCCall_Interruptible, and changes the behavior of the RTS
to not modify the TSO_ flags on the event of an FFI call from
a thread that was interruptible.  It also modifies the bytecode
format for foreign call, adding an extra Word16 to indicate
interruptibility.

The semantics of interruption vary from platform to platform, but the
intent is that any blocking system calls are aborted with an error code.
This is most useful for making function calls to system library
functions that support interrupting.  There is no support for pre-Vista
Windows.

There is a partner testsuite patch which adds several tests for this
functionality.

The instances (and deriving declarations) have been taken from the ghc-syb
package.

It still lives in darcs, if anyone wants to revive it sometime.

First in a series of patches to add the feature.
This patch just adds PrimCallConv to the CCallConv type.

This merge does not turn on the new codegen (which only compiles
a select few programs at this point),
but it does introduce some changes to the old code generator.

The high bits:
1. The Rep Swamp patch is finally here.
   The highlight is that the representation of types at the
   machine level has changed.
   Consequently, this patch contains updates across several back ends.
2. The new Stg -> Cmm path is here, although it appears to have a
   fair number of bugs lurking.
3. Many improvements along the CmmCPSZ path, including:
   o stack layout
   o some code for infotables, half of which is right and half wrong
   o proc-point splitting

Modules that need it import it themselves instead.

Older GHCs can't parse OPTIONS_GHC.
This also changes the URL referenced for the -w options from
WorkingConventions#Warnings to CodingStyle#Warnings for the compiler
modules.

Most of the other users of the fptools build system have migrated to
Cabal, and with the move to darcs we can now flatten the source tree
without losing history, so here goes.

The main change is that the ghc/ subdir is gone, and most of what it
contained is now at the top level.  The build system now makes no
pretense at being multi-project, it is just the GHC build system.

No doubt this will break many things, and there will be a period of
instability while we fix the dependencies.  A straightforward build
should work, but I haven't yet fixed binary/source distributions.
Changes to the Building Guide will follow, too.

ccallConvAttribute: use __attribute__((__stdcall__)) rather than
__stdcall (the latter is Win32-specific).

Merge backend-hacking-branch onto HEAD.  Yay!

Legacy Removal
~~~~~~~~~~~~~~

The following features have been consigned to the bit bucket:

  _ccall_
  _casm_
  ``....''  (lit-lits)
  the CCallable class
  the CReturnable class

Support for interop'ing with .NET via FFI declarations along the
lines of what Hugs98.NET offers, see

 http://haskell.org/pipermail/cvs-hugs/2003-March/001723.html

for FFI decl details.

To enable, configure with --enable-dotnet + have a look
in ghc/rts/dotnet/Makefile for details of what tools are needed to
build the .NET interop layer (tools from VS.NET / Framework SDK.)

The commit doesn't include some library additions + wider-scale
testing is required before this extension can be regarded as available
for general use. 'foreign import dotnet' is currently only supported
by the C backend.

FastString cleanup, stage 1.

The FastString type is no longer a mixture of hashed strings and
literal strings, it contains hashed strings only with O(1) comparison
(except for UnicodeStr, but that will also go away in due course).  To
create a literal instance of FastString, use FSLIT("..").

By far the most common use of the old literal version of FastString
was in the pattern

	  ptext SLIT("...")

this combination still works, although it doesn't go via FastString
any more.  The next stage will be to remove the need to use this
special combination at all, using a RULE.

To convert a FastString into an SDoc, now use 'ftext' instead of
'ptext'.

I've also removed all the FAST_STRING related macros from HsVersions.h
except for SLIT and FSLIT, just use the relevant functions from
FastString instead.

Binary Interface Files - stage 1
--------------------------------

This commit changes the default interface file format from text to
binary, in order to improve compilation performace.

To view an interface file, use 'ghc --show-iface Foo.hi'.

utils/Binary.hs is the basic Binary I/O library, based on the nhc98
binary I/O library but much stripped-down and working in terms of
bytes rather than bits, and with some special features for GHC: it
remembers which Module is being emitted to avoid dumping too many
qualified names, and it keeps track of a "dictionary" of FastStrings
so that we don't dump the same FastString more than once into the
binary file.  I'll make a generic version of this for the libraries at
some point.

main/BinIface.hs contains most of the Binary instances.  Some
instances are in the same module as the data type (RdrName, Name,
OccName in particular).  Most instances were generated using a
modified version of DrIFT, which I'll commit later.  However, editing
them by hand isn't hard (certainly easier than modifying
ParseIface.y).

The first thing in a binary interface is the interface version, so
nice error messages will be generated if the binary format changes and
you still have old interfaces lying around.  The version also now
includes the "way" as an extra sanity check.

Other changes
-------------

I don't like the way FastStrings contain both hashed strings (with
O(1) comparison) and literal C strings (with O(n) comparison).  So as
a first step to separating these I made serveral "literal" type
strings into hashed strings.  SLIT() still generates a literal, and
now FSLIT() generates a hashed string.  With DEBUG on, you'll get a
warning if you try to compare any SLIT()s with anything, and the
compiler will fall over if you try to dump any literal C strings into
an interface file (usually indicating a use of SLIT() which should be
FSLIT()).

mkSysLocal no longer re-encodes its FastString argument each time it
is called.

I also fixed the -pgm options so that the argument can now optionally
be separted from the option.

Bugfix: PrelNames declared Names for several comparison primops, eg.
eqCharName, eqIntName etc. but these had different uniques from the
real primop names.  I've moved these to PrimOps and defined them using
mkPrimOpIdName instead, and deleted some for which we don't have real
primops (Manuel: please check that things still work for you after
this change).

New call attribute on foreign imports, threadsafe.

It indicates that a foreign import can(*) safely be called
concurrently with the continued evaluation of other Haskell
threads, i.e., when the foreign call is made by a Haskell
thread, it won't hinder the progress of other threads.

(*) - if the platform and RTS supports it, it _will be_
invoked concurrently.

Foreign import/export declarations now conform to FFI Addendum Version 1.0

* The old form of foreign declarations is still supported, but generates
  deprecation warnings.

* There are some rather exotic old-style declarations which have become
  invalid as they are interpreted differently under the new scheme and there
  is no (easy) way to determine which style the programmer had in mind (eg,
  importing a C function with the name `wrapper' where the external name is
  explicitly given will not work in some situations - depends on whether an
  `unsafe' was specified and similar things).

* Some "new" old-style forms have been introduced to make parsing a little bit
  easier (ie, avoid shift/reduce conflicts between new-style and old-style
  grammar rules), but they are few, arcane, and don't really hurt (and I won't
  tell what they are, you need to find that out by yourself ;-)

* The FFI Addendum doesn't specify whether a header file that is requested for
  inclusion by multiple foreign declarations should be included only once or
  multiple times.  GHC at the moment includes an header as often as it appears
  in a foreign declaration.  For properly written headers, it doesn't make a
  difference anyway...

* Library object specifications are currently silently ignored.  The feature
  was mainly requested for external calls in .NET (ie, calls which invoke C
  routines when Haskell is compiled to ILX), but those don't seem to be
  supported yet.

* Foreign label declarations are currently broken, but they were already
  broken before I started messing with the stuff.

The code is moderately tested.  All modules in lib/std/ and hslibs/lang/
(using old-style declarations) still compile fine and I have run a couple of
tests on the different forms of new-style declarations.

Add comments

------------------------------------------------------
	More stuff towards generalising 'foreign' declarations
	------------------------------------------------------

This is the second step towards generalising 'foreign' declarations to
handle langauges other than C.  Now I can handle

  foreign import dotnet type T
  foreign import dotnet "void Foo.Baz.f( T )" f :: T -> IO ()



			** WARNING **
	I believe that all the foreign stuff for C should
	work exactly as before, but I have not tested it
	thoroughly.  Sven, Manuel, Marcin: please give it a
	whirl and compare old with new output.


Lots of fiddling around with data types.  The main changes are

* HsDecls.lhs
	The ForeignDecl type and its friends
	Note also the ForeignType constructor to TyClDecl

* ForeignCall.lhs
	Here's where the stuff that survives right through
	compilation lives

* TcForeign.lhs DsForeign.lhs
	Substantial changes driven by the new data types

* Parser.y ParseIface.y RnSource
	Just what you'd expect

-------------------------------------------
	Towards generalising 'foreign' declarations
	-------------------------------------------

This is a first step towards generalising 'foreign' declarations to
handle langauges other than C.  Quite a lot of files are touched,
but nothing has really changed.  Everything should work exactly as
before.

	But please be on your guard for ccall-related bugs.

Main things

Basic data types: ForeignCall.lhs
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Remove absCSyn/CallConv.lhs

* Add prelude/ForeignCall.lhs.  This defines the ForeignCall
  type and its variants

* Define ForeignCall.Safety to say whether a call is unsafe
  or not (was just a boolean).  Lots of consequential chuffing.

* Remove all CCall stuff from PrimOp, and put it in ForeignCall


Take CCallOp out of the PrimOp type (where it was always a glitch)
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
* Add IdInfo.FCallId variant to the type IdInfo.GlobalIdDetails,
	along with predicates Id.isFCallId, Id.isFCallId_maybe

* Add StgSyn.StgOp, to sum PrimOp with FCallOp, because it
  *is* useful to sum them together in Stg and AbsC land.  If
  nothing else, it minimises changes.


Also generally rename "CCall" stuff to "FCall" where it's generic
to all foreign calls.