Changes to ghc(2)

Changes to ghc:
commit 025a66e7fc416ab9ee1df56ad26dfe6232d32900
Author: Austin Seipp <austin@well-typed.com>
Date:   Fri Feb 28 16:28:28 2014 -0600

    Fix binary-dist target with xz/gzip

    This was harmless but annoying: we forgot to take the compression
    extention into account when copying the binary dist out of bindistprep

    Signed-off-by: Austin Seipp <austin@well-typed.com>

commit 71611523c25bb89b81e789d5a2dd3d5d9754b025
Author: Austin Seipp <austin@well-typed.com>
Date:   Fri Feb 28 16:23:17 2014 -0600

    Documentation updates for 7.8.1 release

    Notably, GND is now usable with Safe Haskell. Also, Coercible now is in
    Data.Coerce canonically, and we added some more instances.

    Signed-off-by: Austin Seipp <austin@well-typed.com>