Changes to ghc

Changes to ghc:
commit 2e03d8664bcf39c26537d6cdcb97c3bfe081bb94
Author: Edward Z. Yang <ezyang@cs.stanford.edu>
Date:   Sun May 4 01:18:54 2014 -0700

    Update comment now that we have per-gen weak pointer lists.

    Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>