glXQueryServerString() returns NULL with lsb-Xvfb on Ubuntu 8.10

[Jeff Johnson]

If Xvfb runs on Ubuntu 8.10

/opt/lsb/bin/Xvfb -render -screen 0 1024*768*24 :1.0 -x GLX -ac +bs -kb -fp
/opt/lsb/share/fonts/misc

(as runs in the tests libgl-t2c), then glXQueryServerString() in the code

Display* display = XOpenDisplay(":1.0");
glXQueryServerString(display, 0, GLX_VERSION);

returns NULL.

Also, glXGetFBConfigs(display, 0, &nconfigs) returns NULL, which means that
list of available configs of this display is empty, and one cannot get any
GLContext for use OpenGL functions.

When use native Xvfb everything looks ok - glXQueryServerString(GLX_VERSION)
returns 1.2, and glXGetFBConfigs(display, 0, &nconfigs) return non-empty list
of available configs.

It seems that this is a reason of bug 2406(Qt cannot create GLContext).