naming of directories for the new libraries

[Ross Paterson]

The Hugs counterpart of a package is a directory that can be put in the
search path.  Currently I'm using two:

	libraries - corresponding to the new hierarchical libraries
		packages base, haskell98 and haskell-src
	oldlib - a flat directory corresponding to hslibs and lib/exts

Compilers don't like huge packages, but that doesn't apply to an
interpreter.  Still, maybe we'll need more packages in the future,
so to allow for future expansion I'm thinking of renaming these

	libraries -> libraries/core
	oldlib -> libraries/compat

More to type in -P though (maybe put them in lib?)