This is the SGI libtess library. As a part of Mesa 4.0.2, the SGI
sources for GLU were included. One part of this is libtess and so I want
to merge this into my own build tree so I could use this code without
having to worry about the version of GLU that I might be using (which is
different everywhere and some tesselators are unreliable). These are the
original sources from the Mesa-4.0.2/si-glu/libtess dir.