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   CmmTop -> CmmDecl
   CmmPgm -> CmmGroup

I observed that the [CmmStatics] within CmmData uses the list in a very stylised way.
The first item in the list is almost invariably a CmmDataLabel. Many parts of the
compiler pattern match on this list and fail if this is not true.

This patch makes the invariant explicit by introducing a structured type CmmStatics
that holds the label and the list of remaining [CmmStatic].

There is one wrinkle: the x86 backend sometimes wants to output an alignment directive just
before the label. However, this can be easily fixed up by parameterising the native codegen
over the type of CmmStatics (though the GenCmmTop parameterisation) and using a pair
(Alignment, CmmStatics) there instead.

As a result, I think we will be able to remove CmmAlign and CmmDataLabel from the CmmStatic
data type, thus nuking a lot of code and failing pattern matches. This change will come as part
of my next patch.

This changes the new code generator to make use of the Hoopl package
for dataflow analysis.  Hoopl is a new boot package, and is maintained
in a separate upstream git repository (as usual, GHC has its own
lagging darcs mirror in http://darcs.haskell.org/packages/hoopl).

During this merge I squashed recent history into one patch.  I tried
to rebase, but the history had some internal conflicts of its own
which made rebase extremely confusing, so I gave up. The history I
squashed was:

  - Update new codegen to work with latest Hoopl
  - Add some notes on new code gen to cmm-notes
  - Enable Hoopl lag package.
  - Add SPJ note to cmm-notes
  - Improve GC calls on new code generator.

Work in this branch was done by:
   - Milan Straka <fox@ucw.cz>
   - John Dias <dias@cs.tufts.edu>
   - David Terei <davidterei@gmail.com>

Edward Z. Yang <ezyang@mit.edu> merged in further changes from GHC HEAD
and fixed a few bugs.

 * I've pushed the SPILL and RELOAD instrs down into the
   LiveInstr type to make them easier to work with. 

 * When the graph allocator does a spill cycle it now just
   re-annotates the LiveCmmTops instead of converting them 
   to NatCmmTops and back. 

 * This saves working out the SCCS again, and avoids rewriting
   the SPILL and RELOAD meta instructions into real machine
   instructions.

    
   DO NOT MERGE TO GHC 6.12 branch
   (Reason: interface file format change.)

The typechecker needs to instantiate otherwise-unconstraint type variables to
an appropriately-kinded constant type, but we didn't have a supply of 
arbitrarily-kinded tycons for this purpose.  Now we do.

The details are described in Note [Any types] in TysPrim.  The
fundamental change is that there is a new sort of TyCon, namely
AnyTyCon, defined in TyCon.

Ter's a small change to interface-file binary format, because the new
AnyTyCons have to be serialised.

I tided up the handling of uniques a bit too, so that mkUnique is not
exported, so that we can see all the different name spaces in one module.

 * The old Reg type is now split into VirtualReg and RealReg.
 * For the graph coloring allocator, the type of the register graph
   is now (Graph VirtualReg RegClass RealReg), which shows that it colors
   in nodes representing virtual regs with colors representing real regs.
   (as was intended)  
 * RealReg contains two contructors, RealRegSingle and RealRegPair,
   where RealRegPair is used to represent a SPARC double reg 
   constructed from two single precision FP regs. 
 * On SPARC we can now allocate double regs into an arbitrary register
   pair, instead of reserving some reg ranges to only hold float/double values. 

  - nativeGen/Instruction defines a type class for a generic
    instruction set. Each of the instruction sets we have, 
    X86, PPC and SPARC are instances of it.
  
  - The register alloctors use this type class when they need
    info about a certain register or instruction, such as
    regUsage, mkSpillInstr, mkJumpInstr, patchRegs..
  
  - nativeGen/Platform defines some data types enumerating
    the architectures and operating systems supported by the 
    native code generator.
  
  - DynFlags now keeps track of the current build platform, and 
    the PositionIndependentCode module uses this to decide what
    to do instead of relying of #ifdefs.
  
  - It's not totally retargetable yet. Some info info about the
    build target is still hardwired, but I've tried to contain
    most of it to a single module, TargetRegs.
  
  - Moved the SPILL and RELOAD instructions into LiveInstr.
  
  - Reg and RegClass now have their own modules, and are shared
    across all architectures.

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)

Fixes building with -Werror (i.e. validate) and GHC < 6.6

Track what slots each basic block reloads from. When cleaning spill 
instructions we can use this information to decide whether the slot 
spilled to will ever be read from on this path.

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.