Comment # 65 on bug 110214 from Diego Viola

Just to make it a bit more clear:

If I set that environment variable while I'm already on X:

export MESA_EXTENSION_OVERRIDE="-GL_NV_texture_barrier"

It has no effect on Xephyr (from current git master), i.e. xterm still shows
the bug.

However, if I set before `startx`.

It works with both, X and Xephyr (from git master), i.e. xterm works fine.