Changes to ghc

Changes to ghc:
commit 750271e61bdbaad50c19176406512e79abe404a8
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Fri Apr 4 08:41:35 2014 +0100

    Simplify and tidy up the handling of tuple names

    This fixes Trac #8954.

    There were actually three places where tuple occ-names
    were parsed:
      - IfaceEnv.lookupOrigNameCache
      - Convert.isBuiltInOcc
      - OccName.isTupleOcc_maybe

    I combined all three into TysWiredIn.isBuiltInOcc_maybe
    Much nicer.