Changes to ghc

Changes to ghc:
commit fa5ac96970f99fe463d78ab424514ce28741804a
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Sun Apr 27 19:15:16 2014 +0200

    Don't require mk/config.mk for all cleanup targets

    `make clean` did already ignore a missing mk/config.mk,
    but `make distclean` and `make maintainer-clean` didn't.
    This commit rectifies this oversight.

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