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The section in the building guide was becoming out of date, a wiki
page is much more likely to be kept fresh.

StgBool is mapped to C's int type.  GHC doesn't currently know the
size of a C int on the target arch, it's easier to use StgInt instead.
I guess nobody ever uses Bool arguments to foreign imports/exports.

Fixes #746

GHC does not now do "hoisting" as it used to.  Instead, it allows
foralls to the right of fuction arrows, as well as to the left.

But the type-validity tester hadn't caught up.  This commit fixes 
it. The test is tc203.

Incidentally, GHC still doesn't let you write
	forall a. Eq a => forall b. b -> b
because we get a zillion reduce/reduce errors if we allow that.  I'm
sure it's fixable.  But meanwhile you have to use an auxiliary type
synonym, which is a bit stupid.

'insertStableSymbol' is used for exporting closures that are affected by the GC.

Bulat pointed out that in Template Haskell
   $x
is allowed instead of 
   $(x)
in expressions, but not at the top level of modules.

This commit fixes the omission.  Now you can say

	f x = x
 	$h
	data T = T

and the $h will run Template Haskell just as you'd expect.

If a TH programmer uses a type constructor as a data constructor,
GHC simply crashed.  This commit makes it report the error in a
graceful way.

SpecConstr currently uses substExpr for tiresome reasons to do with
GADTs.  Unfortunately the substExpr generates some WARNINGS (when DEBUG)
is on, because we aren't adding all the in-scope Ids to the in-scope
set of the substitution.

When we move to FC these substExprs will go away, so I'm not going to
worry about this now.

Consider

  data T a where
    T1 :: T Int
    T2 :: T Bool
    T3 :: T Char

  f :: T Bool -> Int
  f x = case x of
	  DEFAULT -> ...
	  T2 -> 3

Here the DEFAULT case covers multiple constructors (T1,T3), but none 
of them can match a scrutinee of type (T Bool).  So we can prune away
the default case altogether.

In implementing this, I re-factored this bit of the simplifier, elminiating
prepareAlts from SimplUtils, and putting all the work into simplAlts in
Simplify

The proximate cause was a program written by Manuel using PArrays

Division by an integral log2 can't be directly optimised to a shift
right, because shift right behaves like a division that rounds to
negative infinity, whereas we want one that rounds to zero.  Fix this
by adding (divisor-1) to the dividend when it is negative before
shifting.  We do this without jumps, generating very slightly worse
code than gcc, which uses conditional moves on CPUs that support it.

Up to now, the silent unwrapping of newtypes in foreign import/export
has been limited to data values.  But it's useful for the IO monad
itself:

	newtype MyIO a = MIO (IO a)

	foreign import foo :: Int -> MyIO Int

This patch allows the IO monad to be
wrapped too. This applies to foreign import "dynamic" and "wrapper", 
thus
   foreign import "wrapper" foo :: MyIO () -> HisIO (FunPtr (MyIO ())) 

Warning: I did on the plane, and I'm no longer sure if its 100% 
complete, so needs more testing.  In particular the wrapper/dynamic bit.

Ross Paterson pointed out a useful generalisation of GHC's 
newtype-deriving mechanism.  This implements it.  The idea
is to allow
	newtype Wrap m a = Wrap (m a) deriving (Monad, Eq)
where the representation type doesn't start with a type
constructor.

Actually GHC already *did* implement this, but the eta-ok
check in TcDeriv missed a case, so there was a lurking bug.

This patches fixes the documentation too.  drvrun019 tests.

We weren't making them live early enough, with the result that
finalizable objects referred to only by a thread blocked on a black
hole could be finalized too early (see conc057 test).

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.