The appended patch
From: Ian Romanick <idr@us.ibm.com> Date: Thu, 13 Jul 2006 15:27:37 +0000 Subject: [PATCH] Move initialization of server_support from __glXProcessServerString to __glXCalcualteUsableExtensions.
should solve the problem. I adjusted the file path to make it applicable to x2go.
Cf. https://bugs.freedesktop.org/show_bug.cgi?id=7353
The patch dates from *** 2006 ***. We definitely should rebase the mesa code.
Best regards
Heinrich Schuchardt