Blender subsystems that care about OpenGL use GL_DEFINITIONS, which now includes the newest (temporary) WITH_LEGACY_OPENGL.
Also updated Gawain's CMake to use this instead of its own logic.
Before now it lived in source/blender/gpu for convenience. Only a few files in the gpu module use Gawain directly.
Tested on Mac, time to push and test on Windows.
Todo: some CMake magic to make it easy to
#include "gawain/some_header.h"
from any C or H file. Main problem here is the many editors that include GPU_immediate.h which includes Gawain's immediate.h -- is there a way to avoid changing every editor's CMakeLists?
