Library re-organisation:

All libraries now live under ghc/lib, which has the following structure:

	ghc/lib/std    		--  all prelude files 		(libHS.a)
	ghc/lib/std/cbits

	ghc/lib/exts		-- standard Hugs/GHC extensions (libHSexts.a)
				-- available with '-fglasgow-exts'

	ghc/lib/posix		-- POSIX library                (libHSposix.a)
	ghc/lib/posix/cbits     -- available with '-syslib posix'

	ghc/lib/misc		-- used to be hslibs/ghc	(libHSmisc.a)
	ghc/lib/misc/cbits	-- available with '-syslib misc'

	ghc/lib/concurrent	-- Concurrent libraries		(libHSconc.a)
				-- available with '-concurrent'

Also, several non-standard prelude modules had their names changed to begin
with 'Prel' to reduce namespace pollution.

	Addr      ==> PrelAddr     (Addr interface available in 'exts')
	ArrBase   ==> PrelArr
	CCall     ==> PrelCCall    (CCall interface available in 'exts')
	ConcBase  ==> PrelConc
	GHCerr    ==> PrelErr
	Foreign   ==> PrelForeign  (Foreign interface available in 'exts')
	GHC       ==> PrelGHC
	IOHandle  ==> PrelHandle
	IOBase    ==> PrelIOBase
	GHCmain   ==> PrelMain
	STBase    ==> PrelST
	Unsafe    ==> PrelUnsafe
	UnsafeST  ==> PrelUnsafeST