Changes to ghc

Changes to ghc:
commit dc4b66f6f266518ff9238edbe94c89702e98b8ad
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Fri Apr 18 12:31:51 2014 +0200

    Update Cabal submodule to fix Solaris build

    see also https://github.com/haskell/cabal/issues/1789