dumb down our CPP so that it works in both traditional and ansi modes

This patch looks big and onerous but you really only need to understand the changes in HsOpenGLRaw.h. Everything else is just an automatic change that could be done with sed (I used vim macros) to add the two new parameters to `EXTENSION_ENTRY` everywhere it's used.

I tested the changes on:

  * OSX Mavericks
    * 7.6.3 from homebrew, uses gcc instead of clang for CPP
    * 7.8.2 built from source, uses clang instead of gcc (previously failed with a parse error)
  * Windows 7 64bit with 7.8.2 64bit.
  * Linux + lots of ghc versions via travis-ci, details: https://travis-ci.org/dagit/OpenGLRaw/builds/24942160

While this change is not optimal, I think it's a reasonable compromise that lets us fix #18 and #21.