re-add the GNUmakefiles

[Simon Marlow]

Mon Jan 23 03:52:36 PST 2006  Simon Marlow <simonmar at microsoft.com>
  * re-add the GNUmakefiles
  These are now safe after we added "-f Makefile" to the make args when invoked
  from the GHC build system.  This repo should now be useable as the main
  Cabal repo.

    A ./GNUmakefile
    A ./doc/GNUmakefile