Infrastructure. It allows customizing performance and visual quality
settings of OpenGL drivers on a per-driver, per-screen and/or
per-application level.
The settings are stored in system wide and per-user XML configuration
files, which are parsed by the OpenGL drivers on startup.
Originally by oga@; tested by oga@ and guenther@. Python jiggery and
other cleanups by moi.
double ok fgsch@, ribbit landry@
