The problem was that when loading interface files in checkOldIface, we
were not passing the If monad the mutable variable for use when
looking up entities in the *current* module, with the result that the
knots wouldn't be tied properly, and some instances of TyCons would
be incorrectly abstract.

This bug has subtle effects: for example, recompiling a module without
making any changes might lead to a slightly different result (noticed
due to the new interface-file fingerprints).  The bug doesn't lead to
any direct failures that we're aware of.

o Moved BlockId stuff to a new file to avoid module recursion
o Defined stack areas for parameter-passing locations and spill slots
o Part way through replacing copy in and copy out nodes
  - added movement instructions for stack pointer
  - added movement instructions for call and return parameters
    (but not with the proper calling conventions)
o Inserting spills and reloads for proc points is now procpoint-aware
  (it was relying on the presence of a CopyIn node as a proxy for
   procpoint knowledge)
o Changed ZipDataflow to expect AGraphs (instead of being polymorphic in
   the type of graph)

For clients that forget to do hs_add_root()

Several changes in this patch, partially bug fixes, partially new code:
o bug fixes in ZipDataflow
   - added some checks to verify that facts converge
   - removed some erroneous checks of convergence on entry nodes
   - added some missing applications of transfer functions
o changed dataflow clients to use ZipDataflow, making ZipDataflow0 obsolete
o eliminated DFA monad (no need for separate analysis and rewriting monads with ZipDataflow)
o started stack layout changes
   - no longer generating CopyIn and CopyOut nodes (not yet fully expunged though)
   - still not using proper calling conventions
o simple new optimizations:
   - common block elimination
      -- have not yet tried to move the Adams opt out of CmmProcPointZ
   - block concatenation
o piped optimization fuel up to the HscEnv
   - can be limited by a command-line flag
   - not tested, and probably not yet properly used by clients
o added unique supply to FuelMonad, also lifted unique supply to DFMonad

This is a much more robust way to do recompilation checking.  The idea
is to create a fingerprint of the ABI of an interface, and track
dependencies by recording the fingerprints of ABIs that a module
depends on.  If any of those ABIs have changed, then we need to
recompile.

In bug #1372 we weren't recording dependencies on package modules,
this patch fixes that by recording fingerprints of package modules
that we depend on.  Within a package there is still fine-grained
recompilation avoidance as before.

We currently use MD5 for fingerprints, being a good compromise between
efficiency and security.  We're not worried about attackers, but we
are worried about accidental collisions.

All the MD5 sums do make interface files a bit bigger, but compile
times on the whole are about the same as before.  Recompilation
avoidance should be a bit more accurate than in 6.8.2 due to fixing
#1959, especially when using -O.

Now you just add them to SUBDIRS_BUILD instead of SUBDIRS.

You need to use the build.* rules rather than the make.* rules, though.

- When compiling with -mmacos-deployment-target=10.4, we need 
  --no-builtin-fprintf, as the use of GCC's builtin function 
  optimisation for fprintf together with #include "PosixSource" in the 
  RTS leads to the use of fwrite$UNIX2003 (with GCC 4.0.1 on Mac OS X 
  10.5.2).

	as discussed in this thread:
	http://www.haskell.org/pipermail/glasgow-haskell-users/2008-April/014614.html

This fixes a segfault in #1657

In an instance declaration, omitted methods get a definition that
uses the default method.  We used to generate source code and feed it
to the type checker.  But tc199 shows that is a bad idea -- see
Note [Default methods in instances] in TcClassDcl.

So this patch refactors to insteadl all us to generate the 
*post* typechecked code directly for default methods.

Refactoring reduces code and improves error messages

This bug allowed, for example

  f = let x = ( 1#, 'x' ) in x

which is ill-typed because you can't put an unboxed value in a tuple.
Core Lint fails on this program.

The patch makes the program be rejcted up-front.

Now we use <prog>.hp and <prog>.prof consistently.

This is the optimisation level recommended when compiling DPH programs. At the
moment, it is equivalent to -O2 -fno-method-sharing -fdicts-cheap
-fmax-simplifier-iterations20 -fno-spec-constr-threshold.

We want -Odph to be a dynamic flag and that should imply -fno-method-sharing.
This doesn't add a lot of complexity.