Changes to ghc

Changes to ghc:
commit 32f41c79960ffc1d04c4573acb37756109d279a5
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Wed Feb 26 22:20:52 2014 +0100

    Make distribution tarball compression format configurable

    By default, bzip2 compression is selected (which is what has been used
    till now). Additionally, by setting the TAR_COMP make variable to one of
    the values "bzip2", "gzip", or "xz", an explicit compression format can
    be requested for the distribution tarballs. For instance, invoking

      make TAR_COMP=xz sdist-ghc

    will result in a tarball `./sdistprep/ghc-7.9.20140226-src.tar.xz`

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