Changes to ghc

Changes to ghc:
commit 1cf0c8ad321d1d358cbec46d35be02566faf2d00
Author: Jan Stolarek <jan.stolarek@p.lodz.pl>
Date:   Thu Oct 17 23:17:06 2013 +0200

    Optimise stack checks that are always false

    Fix a bug introduced in 94125c97e49987e91fa54da6c86bc6d17417f5cf.
    See Note [Always false stack check]