Changes to ghc

Changes to ghc:
commit dbe0b8c28b846224fc6226e24780999dd88ea3ef
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Thu Apr 17 16:12:23 2014 +0200

    Update Cabal submodule to latest tip of 1.20 branch

    The testsuite reference output for ghcpkg01 needs to be adapted
    since a "More diff friendly pretty printing of cabal files"
    is now performed.