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	MERGE TO 6.6 branch!

Some while ago I made the type checker a tiny bit more lenient about
left sections, so that 
	(x !)
would typecheck iff
	((!) x) 
typechecks.  

Strictly, Haskell 98 requires that the section typechecks iff
	(\y. (!) x y)
typechecks, and I should really have made the relaxation dependent on a 
flag, but I didn't.

Anyway, this commit fixes the *desugarer* so that it correctly desugars
the programs that the typechecker passes.

When fiddling with pattern-matching for unboxed tuples, I'd messed up
the slightly-tricky tests for pattern matching on unboxed tuples, notably
	case (# foo, bar #) of r -> ...r...

The fix is in TcPat, and test are tcfail115, tcfail120, and tc209

Spotted by Bulat Ziganshin.

We need the #line directives left in, so that Haddock can figure out
what the name of the original source file was called, which is
necessary for generating source links.  You probably now need an
updated Haddock to generate HTML from the libraries, but a release
will be forthcoming shortly.

The handling of top-level names in declaration brackets is a bit tricky.
This commit fixes Trac #977;  test is TH_spliceD2.

The changes are commented in RnExpr.rnBracket and RdrName.hideSomeUnquals

first, I got the dependencies wrong (should be the .o file, not the
.hs), and secondly GHC's recompilation checker refuses to recompile
these files anyway.  I haven't done anything about the second problem
yet, except to comment it.

Some diffs don't understand --strip-trailing-cr.

I had failed to remove the bit where result type signatures bind
lexical type variables.  And now we are planning to remove them entirely.

This commit therefore does a partial removal (to avoid destablising 6.6).
It also arranges that
	f :: sig = rhs
means a *pattern* binding (not a function binding with no arguments 
and a result signature), which makes sense.

Our .depend machinery doesn't automatically generate these, so we have
to add them manually.  (this fixes one instance of missing
dependencies in the GHC build tree, there are lots more...).

These closure types aren't used/needed, as far as I can tell.  The
commoning up of Chars/Ints happens by comparing info pointers, and
the info table for a dynamic C#/I# is CONSTR_0_1.  The RTS seemed
a little confused about whether CONSTR_CHARLIKE/CONSTR_INTLIKE were
supposed to be static or dynamic closures, too.

Not having this check led to strange error messages.
See test rnfail046.

exprIsCheap was already making record selection look cheap, esp for
dictionary selection; e.g.
   (==) dEq

The idea is to allow those record selections to migrate inside a
lambda, because on the whole it's more expensive to share than 
repeat them.

But sometimes dictionary selection is nested; e.g.
   (==) ($p1Num dNum)

This turned out to make a (fragile) rewrite rule fire a little
more robustly, but it seems like a good idea in any case.

This patch makes nested record selections also look cheap.

GHC's design for lexically scoped type variables has changed.
Here, belatedly, is the documentation.