Changes to ghc

Changes to ghc:
commit 35d95a2abe944f8c51c9faf798a404f458bc2ad2
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Sun Apr 20 17:31:34 2014 +0200

    Update submodule to final Cabal-1.20.0.0 release

    Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>