* Similar to the OpenAL URA, OpenGL calls are now made to an interface
which is implemented by the backends
* Major cleanups in the texture util code to handle GLES2 texture formats
* Split the GL interface into several interfaces depending on API and version:
- GL (common denominator for all GL APIs)
- GL2 (desktop GL2)
- GL3 (desktop GL3)
- GLFbo (framebuffer object functions)
- GLExt (desktop GL and OpenGL ES extensions)
* Added GLTracer class which traces OpenGL calls made by the engine when activated