Less OES in opengles

Because of things explained in the debian bug [754397](https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=754397), the compilation of mnit project fails on linux systems with a recent mesa library.

One way to solve the problem is to not rely on OES symbols that cause problem.
Fortunately, is seems that classes and methods that use those are unused and/or tagged broken, so just remove them.