Correctly create GLES contexts with GLX/WGL
Earlier commits reworked the necessity of ARB_create_context, creating a few bugs. This series addresses the issues and adds functional tests, to ensure they don't happen again.
The last commit adds a workaround for GLX+OpenGL version test, as needed on one of my machines. I'm suspecting the issue to be specific to my setup, but haven't quite tracked it down.