Changes to ghc

Changes to ghc:
commit 8f831ec578d22419788542290e164c50524d90f6
Author: Dr. ERDI Gergo <gergo@erdi.hu>
Date:   Sun Apr 6 21:26:46 2014 +0800

    Require PatternSynonyms language flag when encountering a use of pattern synonym
    (#8961)