OpenGL_vertex:
* bufferize a duplicate calcul
* Factorize vertexes

This reverts commit 148fffb0.

OpenGL_vertex:
* bufferize a duplicate calcul
* Factorize vertexes

Pass drawtype and material type to shaders.
Move shaders generation to startup only.
Allow assign shaders per tile.
Initial code to support water surface shader.

Parallax mapping with slope information.
Overriding normal maps.