Changes to ghc

Changes to ghc:
commit fbdebd30b9ff3ca76243791723b85959c6860083
Author: Guido Zayas <guido.zayas@gmail.com>
Date:   Fri Jun 6 18:34:14 2014 +0200

    supress warning of bang wildcard pattern-binding (i.e. let !_ = rhs). This fixes #9127