their drivers can't do anything useful like report an error; they just
silently screw up. Limiting it to 31 makes it work, but there's still a
strange slowdown issue (and it's not that the shaders are being run in
software, but it's worth checking for that anyway).
git-svn-id: svn+ssh://src.earth.threerings.net/nenya/trunk@243 ed5b42cb-e716-0410-a449-f6a68f950b19
Andrzej Kapolka
6b07087c31