Fixed up version of the OpenGL ARB shader "parallax map and normal map with fog" patch. The code requires little changes to the ShaderMaterial in order to reuse existing shader renders, as we now have an array instead of one shader handle. Also, vertex and pixel shaders need to be adapted for fog usage, namely by setting the fogcoord in the vertex shader and adding a comment into which Irrlicht will add the proper fog option. Documentation will follow once we have cleaned up the shader usage.

git-svn-id: svn://svn.code.sf.net/p/irrlicht/code/trunk@2467 dfc29bdd-3216-0410-991c-e03cc46cb475