patch applied (ghc-6.12/ghc): MERGED: libffi: install 'ffitarget.h' header as sole 'ffi.h' is unusable

[Ian Lynagh]

Tue Mar 30 07:50:54 PDT 2010  Ian Lynagh <igloo at earth.li>
  * MERGED: libffi: install 'ffitarget.h' header as sole 'ffi.h' is unusable
  Simon Marlow <marlowsd at gmail.com>**20100329135734

    M ./libffi/ghc.mk -1 +5