Changes to ghc

Changes to ghc:
commit 3099e40d2737172c746a6456ddcd34b54e120aa0
Author: Iavor S. Diatchki <iavor.diatchki@gmail.com>
Date:   Mon Mar 17 23:19:16 2014 -0700

    Add some documentation about type-level literals.

    I moved the "promoted literals" sub-section into a separate section,
    as many folks were not finding the docs.  I also added some additional
    paragraphs describing the current state of the feature.