Changes to ghc

Changes to ghc:
commit b626c3d4ce0e66216705ba8355c914dc809e3fe7
Author: Austin Seipp <austin@well-typed.com>
Date:   Mon Feb 17 06:48:04 2014 -0600

    Add comments explaining #8754

    Signed-off-by: Austin Seipp <austin@well-typed.com>