Changes to ghc

Changes to ghc:
commit f964cd9c5c411f8a2383cf2b080581a5c3349661
Author: Simon Peyton Jones <simonpj@microsoft.com>
Date:   Fri Apr 18 23:30:18 2014 +0100

    Take account of the AvailTC invariant when importing

    In the rather gnarly filterImports code, someone had forgotten
    the AvailTC invariant:  in AvailTC n [n,s1,s2], the 'n' is itself
    included in the list of names.