Changes to ghc

Changes to ghc:
commit ab3f95bdfc5c001c7dd3158c52bad604d28aabf3
Author: Joachim Breitner <mail@joachim-breitner.de>
Date:   Sat Jun 7 09:57:32 2014 +0200

    s/-hi-diffs/-ddump-hi-diffs/ in docs (#9179)