GHC platforms

[Simon Marlow]

I've put up a wiki page listing the platforms that GHC supports and
which features are supported on each platform:

  http://hackage.haskell.org/trac/ghc/wiki/Platforms

I've no doubt made mistakes and there are a few empty boxes where I
wasn't sure.  Please improve the information here if you can.  This
replaces the section in the Building Guide that was becoming rather out
of date.

Cheers,
	Simon