Derived from 
https://cgit.freedesktop.org/mesa/glu/
commit 0bf42e41c8b63fc2488dd8d41f696310b5a5a6a7
Fri Jun 10 05:30:00 2016

This directory contains just the libtess tesselation library to be statically compilable without OpenGL dependencies.
Only the following functions are provided, and mangled:

mgluNewTess
mgluDeleteTess
mgluTessBeginPolygon
mgluTessBeginContour
mgluTessVertex
mgluTessEndPolygon
mgluTessEndContour
mgluTessProperty
mgluTessNormal
mgluTessCallback
mgluGetTessProperty
mgluBeginPolygon
mgluNextContour
mgluEndPolygon

Do include gl.h, glu.h or glut.h together with glu-libtess.h, you would get symbol clashes!