Make sure to set all sources at once (glShaderSource replaces).
Handle shader being deleted before detach (just drop the detach)
Implement AllowFullscreen (or rather, !AllowFullscreen) for win32 GL
Serialise transform feedback buffer bindings into feedback record
Special case GL_POINTS as it's enum value 0 (shows as GL_NONE)
Consider buffers that are bound to xfm feedback to be dirty