[MP] Rend2: Remove explicit fragment out locations

This commit removes the explicit layout location qualifiers from some
fragment shaders as these are not available in OpenGL 3.2. They are
replaced with API calls to glBindFragDataLocation to set their locations.
[MP] Rend2: Remove #version directive

The #version directive is added programmatically by the renderer. They
shouldn't be placed in the GLSL files.