Log Message:
Update happy to version 1.16; changes since 1.15:

 * Switch to a Cabal build system: you need a recent version of Cabal
  (1.1.6 or later).  If you have GHC 6.4.2, then you need to upgrade
   Cabal before building Happy.  GHC 6.6 is fine.

 * New %error directive

 * New production forms: {%% .. } and {%^ .. }

 * Added Attribute Grammar support, by Robert Dockins