Changes to ghc-prim

Changes to ghc-prim:
commit 3a0a55861bcd9c20f33c468d51e65065fdd83c5f
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Sun Oct 27 16:29:28 2013 +0100

    Add overlooked language extensions to `IntWord64.hs`

    This was overseen in b07b88e5d5c3ccd1508b235688f751408636c49e
    as the extensions are only needed when compiling for 32-bit archs.

    Signed-off-by: Herbert Valerio Riedel <hvr@gnu.org>