Distant geometry

A few shaders (for now, ksPerPixel, ksPerPixelAT, ksPerPixelNM, ksMultilayer and  ksMultilayer_fresnel_nm) got an option to get rid of distant clipping, set in track config. The idea is to “squish” geometry alongside view direction in such a way that it wouldn’t affect fog, lighting or any other visual things. Just get rid of clipping. 

Not quite sure that there aren’t any flaws I missed, but it seems to be working great so far. Extra FX wouldn’t affect those distant meshes (for it, it’s like part of the sky), but I don’t think something located in 20+ km needs things like local reflections.