Changes to ghc

Changes to ghc:
commit a52bf967bbdc5698bb1e4014de2cee9dee494f50
Author: Edward Z. Yang <ezyang@cs.stanford.edu>
Date:   Thu Jun 19 15:58:42 2014 +0100

    Finish the rest of the writeup.

    Signed-off-by: Edward Z. Yang <ezyang@cs.stanford.edu>