Changes to ghc(2)

Changes to ghc:
commit d14e5bf387860d338b3b693453ebe4126a4b2765
Author: Edsko de Vries <edsko@well-typed.com>
Date:   Sun Dec 1 13:55:07 2013 +0000

    Export getHscEnv from HscMain

commit 586bc85538cf12048137c2693da7c9fe3ca481ef
Author: Edsko de Vries <edsko@well-typed.com>
Date:   Thu Nov 28 16:38:26 2013 +0000

    Mask async exceptions in forkM_

    See #8006 for the reason why. This is not a fix as such; more of a workaround.