GL/capabilities.c: Add handleDepthModes(), and extend
handleRendererDescription() for the various depth and multisampling flags.
Add initialization of the new config options to initConfig().
GL/capabilities.h: Add depth and multisample config members.
GL/visualConfigs.c: Add depth and multisampling support to the visual config
setup.
(cherry picked from commit f527381eea)
This gives us a *lot* more visuals, and they should be more accurate.
Some of the visuals may have been wrong before. This may enable more
OpenGL programs to behave correctly.
I also suspect libGL needs a little work to handle some of these correctly.
(cherry picked from commit 98a084ce9c)
