Changes to ghc

Changes to ghc:
commit b1436f55da2b0e005ac09be6651a2c4d934027ec
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Mon May 26 15:25:30 2014 +0100

    Fix yet another bug in 'deriving' for polykinded classes (Trac #7269)

    This patch makes the code a bit simpler if anything.