c15c8facfe
Track the stereo status of windows using the new EXT_stereo_tree GLX extension. When stereo is enabled or disabled, a restart is triggered via meta_restart() after a timeout, setting a _META_ENABLE_STEREO property on the root window to indicate whether we should turn on a stereo stage for clutter. The property avoids a loop, since we need to enable stereo *before* initializing Clutter and GL, but we need GL to figure out whether we have stereo windows. Stereo windows are drawn to the stage using new functionality in Cogl to setup a stereo context, select which buffer to draw to, and draw either the left or right buffer of a stereo texture_from_pixmap.