lib/mnit/opengles1.nit: remove unused part that rely on _OES symbols

Signed-off-by: Jean Privat <jean@pryen.org>
lib/mnit/opengles: cleanup C dependencies.

Signed-off-by: Jean Privat <jean@pryen.org>
Merge: 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 the OES symbols that cause the issue.
Fortunately, it seems that classes and methods that use those symbols are unused and tagged broken, so just remove them.

Closes #689
Closes #677

Pull-Request: #694
Reviewed-by: Alexis Laferrière <alexis.laf@xymus.net>