Pass -lpthread to linker when using a 'threaded' RTS

- new option --enable-threaded-rts, which turns on
  RTS support for better interop with native threads.
- check for pthread.h
- new config.mk variable, GhcRtsThreaded (={YES,NO})

got tired of seeing gcc trigraph warning

Add a short section on modules & packages.

-----------------------------
	Tidy up the top level of TcModule
	-----------------------------

This commit started life as sorting out the TcInstDcls thing that
we got wrong a few weeks back, but it spiraled out of control.

However, the result is a nice tidy up of TcModule.

typecheckModule/tcModule compiles a module from source code
typecheckIface/tcIface   compiles a module from its interface file
typecheckStmt		 compiles a Stmt
typecheckExpr		 compiles a Expr

tcExtraDecls is used by typecheckStmt/typecheckExpr
	to compile interface-file decls.
	It is just a wrapper for:

tcIfaceImports, which is used by tcExtraDecls and tcIface
	to compile interface file-file decls.

tcImports, is similar to tcIfaceImports, but is used only by tcModule

tcIfaceImports is used when compiling an interface, and can
	therefore be quite a bit simpler

Improved printing

Fix markup bug.

comsetic only: shorten some lines.

Simplify the package story inside the compiler.  The new story is
this:

  The Finder no longer determines a module's package based on its
  filesystem location.  The filesystem location indicates only whether
  a given module is in the current package or not (i.e. found along
  the -i path ==> current package, found along the package path ==>
  other package).

  Hence a Module no longer contains a package name.  Instead it just
  contains PackageInfo, which is either ThisPackage or AnotherPackage.
  The compiler uses this information for generating cross-DLL calls
  and omitting certain version information from .hi files.

  The interface still contains the package name.  This isn't used for
  anything right now, but in the future (when we have hierarchical
  libraries) we might use it to automatically determine which packages
  a binary should be linked against.  When building a package, you
  should still use -package-name, but it won't be fatal if you don't.

The warning/error about package name mismatches has gone away.

Set $(HC) *after* including boilerplate.mk, which re-defines it.

Don't use :: rules for building HSstd.o, they cause it to be rebuilt
every time.  According to the GNU make manual, :: rules are vary
rarely actually useful, and I'm sure we use them too much.

Minor cleanups.

Cleanup sweep, we can now use more of the std fptools build system
machinery in here.

- .hsc sources can generate .hc files too
- Fix the sense of a conditional

Fix debug build.

Oops, better not pre-compute PRE_SRCS in paths.mk, because ALL_DIRS is
not set yet.  Instead, defer it until we include target.mk.

Clean up this Makefile:

  - Use the enhanced automatic source-finding machinery from
    paths.mk rather than rolling our own,

  - Turn on UseGhcForCc to get our C files compiled with GHC.
    This fixes some obscure bugs caused by the fact that we
    were re-initializing $(CC_OPTS) in this Makefile using
    :=, when it had previously already been set with = (apparently
    different versions of GNU make behave differently presented
    with this kind of mixed assigment).

GHC_CC_OPTS is a derived version of CC_OPTS with -optc prepended to
each option.  This is used when $(UseGhcForCc) = "YES" (see suffix.mk).

Introduce a new tweakable $(UseGhcForCc) which if set to "YES" enables
a different set of suffix rules which build C-ish files using $(HC)
instead of $(CC).  We'll use this to clean up the ghc/rts Makefile.

- Consider .hc files as real sources unless they are derived from
  .hs/.lhs sources (using the existing "derived sources" mechanism").

- Set PRE_SRCS using := rather than =, to avoid re-expanding the
  $(wildcard) multiple times.  In a simple test I did, this can save
  a 1/4 second (depending on the size of the directores involved) per
  make!

Fix syntax error in printing indirect calls in sparc assembly.

- Allow sources from multiple subdirectories to be selected, by
  setting $(ALL_DIRS).

- Automatically detect Happy sources in the same way as other kinds
  of sources.

cope with the fact that StgTickyHeader is no more

Add ObjectIO to standard packages

Add ProjectPatchLevel

StgParHeader&StgTickyHeader vestige removal

sigh, steer clear of mingw backquoting issues

Add instance Eq Exception (and hence instance Eq IOError).

x86 only: remove special ccall support for calling PerformGC_wrapper
using dodgy-looking calling convention.  PerformGC_wrapper was last
seen alive in GHC 3.X, AFAIK.

Remove some empty structs that weren't used.  Apparently empty structs
are illegal C.

sparc NCG fixes for f-i-dynamic.

Remove StgParInfo - not used anywhere.

Remove PAR_ITBL_SIZE - not used anywhere.

Inline mpz_cmp_si() into cmpIntegerInt#, and mpz_cmp() into cmpInteger#
to offset recent performance degradation caused by outlining of these
primitives.

Also remove heap checks in these primitives: they don't do any
allocation, so no heap check is necessary.

Fix highly obscure bug.

The heap check in cmpIntegerzh_fast was erroneously passing
cmpIntegerIntzh_fast as the resumption point instead of
cmpIntegerzh_fast, with the result that if a heap-check happened to
strike in cmpIntegerzh_fast then we would end up resuming in
cmpIntegerIntzh and returning an incorrect comparison result.  One
symptom is that very occasionally floating point numbers would print
incorrectly (ending in an 'a').

Teach the NCG how to do f-i-dynamic.  Nothing unexpected.
sparc-side now needs fixing.

Allow constructors with non-ptr fields to be allocated in-line.

------------
	Rule phasing
	------------

This commit adds a little more control to when rules are enabled.

  {-# RULES
       "foo" [2] forall ...
       "baz" [~2] forall ...
  #-}

Rule "foo" is active in phase 2 and later.  The new thing is that the
"~2" means that Rule "baz" is active in phase 3 and earlier.
(Remember tha phases decrease towards zero.)

All the machinery was there to implement this, it just needed the syntax.


Why do this?  Peter Gammie (at UNSW) found that rules weren't firing
because of bindings of the form

	M.f = f
	f = ....

where the rules where on the M.f binding.  It turned out that an old
hack (which have for some time elicited the harmless "shortMeOut" debug
warnings) prevented this trivial construction from being correctly
simplified.  The hack in turn derived from a trick in the way the
foldr/build rule was implemented....and that hack is no longer necessary
now we can switch rules *off* as well as *on*.


There are consequential changes in the Prelude foldr/build RULE stuff.
It's a clean-up.... Instead of strange definitions like
	map = mapList
which we had before, we have an ordinary recursive defn of map, together
with rules to convert first to foldr/build form, and then (if nothing
happens) back again.

There's a fairly long comment about the general plan of attack in
PrelBase, near the defn of map.

Update comments re: reloc overflow. A careful re-read of the PE
spec did prove useful; Sec 4.1 (last para) describes how overflow
is handled.

PEi386/COFF: handle relocation overflows, i.e., if a section is
marked with the flag (MY)IMAGE_SCN_LNK_NRELOC_OVFL, then
the first entry in the relocation table holds the 32-bit
relocation count rather than 16-bit number in the section header.
Apparently, a version of the MS PE spec exists that spells this
out, but haven't been able to locate it (perhaps people on the
'inside' could try to locate an up-to-date version...?) winnt.h
is clear enough about it though (as is the GNU libbfd sources).

This is the Right Way to compute the relocation count, but
unfortunately libbfd / GNU ld is generating bogus output
when the reloc field overflows (causing objdump/nm etc. to
crash when trying to read the generated output!) Looking into it.

Once this has been cleared up/fixed, the splitting up of HSstd.o
(and HSwin32.o) should be a thing of the past. I've taken the
liberty of disabling the suspiciously-large-reloc-section test
already.