-RM-123-MR-Use included shaders as own Programs instead of text-replacement (or ensure proper line numbering)
Currently, we have the #include keyword in GLSL files. This inserts the code from the included file there. This is ugly and prohibits proper error output.
We need to abandon this by using osg::Program for each included code which then gets linked together.
(from redmine: created on 2012-01-10, closed on 2014-01-24)