Changes to ghc ghc-prim

Changes to ghc:
commit 1e36a386042248523de69ad6b02c43a6631ed5d0
Author: Joachim Breitner <mail@joachim-breitner.de>
Date:   Fri Mar 14 12:51:37 2014 +0100

    Document Coercible in the user guide

    as a subsection of "Equality constraints", containing references to the
    module's haddock and to the paper. Fixes #8888

Changes to ghc-prim:
commit fc7aaf57a33ab07b70628c75fcf134fdf4e701e5
Author: Joachim Breitner <mail@joachim-breitner.de>
Date:   Fri Mar 14 12:41:46 2014 +0100

    Refer to the coercible paper in Coercible' docs

    Implements parts of #8888.