Blender Git Loki

Fix for #2034

It appeared that the method as used in unified render for "render all sub-
pixels" isn't very well resistant to having large amounts of faces in a
single pixel. The bug file had about 16x70x2 faces per pixel... causing
tremendous slowdown and even wrong render.

I've disabled the option (was coded by Nzc in NaN days) and made it
sampling in the main render loop. Goes much faster, error free. Only loss
is in that it doesnt use superiour subsamples for gauss anymore. Here the
normal render performs slightly better. Not a real issue though. Hard to
notice.