more cleanup :
- consolidate cmake compile flags
- turn on -Wall
- suppress hidden overloaded function warning when using Clang
  (part of it is bug, part of it will require code refactoring
  on our end)
- add support for Maya 2013.5 for windows in cmake module
- clean up some glew includes which break builds with MSVC Express
  & Windows SDK
- move the bitmap for font_image into a compiled object
- remove some unused variables and other minor warnings

Note : this is a checkpoint, there are still a few more warnings to clean up...

fixes #96
Merge branch 'master' of github.com:PixarAnimationStudios/OpenSubdiv