Derived from X.org commit...

 commit 28b95fd9d1c2f078aaaac75c310a27b17c74a6fc
 Author: Kristian Høgsberg <krh@redhat.com>
 Date:   Thu Jul 6 03:25:38 2006 -0400

    Drop unused GL/include subtree.

    Woo, less Makefile's to generate.
Backported-to-NX-by: Mike Gabriel <mike.gabriel@das-netzwerkteam.de>