Changes to ghc

Changes to ghc:
commit 732aa7e24e644928891431d321da52ca6df28a7f
Author: Herbert Valerio Riedel <hvr@gnu.org>
Date:   Sat Mar 1 09:10:32 2014 +0100

    Update to latest Cabal 1.18 branch tip (again)

    This was already performed in 37d6e2c54f117 but accidentally
    reverted as a side-effect of 9976c2ece3aa4.

    So this update pulls in the fix into ghc-7.8 for #8266 again.

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