Changes to ghc

Changes to ghc:
commit faddad7ec6e5738987d5571ad23054a5aa39c193
Author: Duncan Coutts <duncan@well-typed.com>
Date:   Tue Jun 10 13:50:59 2014 +0100

    Improve the API doc description of the SmallArray primitive types

    Say how it differs from Array in terms of size and performance.
    These are primitives so it's also ok to talk a bit about implementation
    details like card tables.