Xephyr with DRI/DRI2

[Feng, Haitao]

Hi,

In May I have submitted code patches to enable DRI2 extension for Xephyr. In
that patch, I have preferred to use DRI extension to get OpenGL acceleration,
and if there is no DRI extension, I will use DRI2 extension. To enable DRI2
extension, some files are added and the basic logics are the same with DRI
except the name "DRI" is changed to "DRI2" in those files.

I'd like to know whether we need DRI extension in Xephyr. If DRI is not
supported in the future, I could change the dri files directly instead of adding
more files into the Xephyr folder.

Thanks
-Haitao