More recent versions of glxcmds.c already do this.
This enables glxinfo to correctly detect the multisampling with output like so
from glxinfo -v:
multiSample=6 multiSampleBuffers=1
(cherry picked from commit 5bc78b9f96)
It was accidentally lost when factoring out __glXDRIdoReleaseTexImage, so this
is a regression fix and should probably be backported to server-1.5-branch.
(cherry picked from commit a4d62bbf21)
GLX is enabled by default, but the current swrast behaviour causes X
to abort with fatal error if the swrast dri library dlopen fails.
Handle the case where the swrast library is not present, and do not
register the GLX extension unless at least one screen has a usable
GL provider.
(cherry picked from commit eff25430b4)
