The xlibmesa-gl1-dri-trunk package available through
apt-get is missing a libGL.so symlink. I had to
manually create it before OpenGL would work. Should be
simple enough to fix.
Oh, and there doesn't seem to be a GL -dev package
available that doesn't conflict with dri-trunk, so I
had to manually install some headers before I could
compile anything with dri-trunk installed.