Changes to ghc

Changes to ghc:
commit 1aeea208f042cf7e4e87ac5444398ac689cac99d
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Fri May 23 07:47:17 2014 +0100

    Make the unifier a fixpoint even for the free kind vars of a tyvar

    The (pure) unifier tcUnifyTys returns an idempotent substitution.
    But previously the kinds of type variables free in the range of
    the subst could have un-substituted kind variables.

    This patch fixes that, fixing Trac #9106.

    See Note [Finding the substitution fixpoint] in Unify

    (cherry picked from commit d8d97113c24e7216be36c9cdfc58e91f26528f06)