Blender Git Loki

SSAO works again. Unfortunately it's unavoidable to have it work without
explicit attenuation control (by using just max distance).

Also it now supports orthographic cameras properly. The maximum distance is
now defined in world space units so it should be slightly easier to understand
and uniform across perspective and orthographic cameras.

The optimizations can be generalized for orthographic cameras but the code is
more complex and the runtime advantage is questionable in that case
(in the end a matrix transform is 4 dot products which are not that terrible)
so commented out the code there for now.