Blender Git Loki

Alleviate grid creating shadows in Ambient Occlusion effect.

Draw the grid last with depth masking disabled. That should have no ill
effects otherwise as far as I can tell except from some exceptional
cases (axis lines over grid) but this is hardly annoying.

Generally to properly solve such issues we need to have a better render
pipeline with wire objects/materials being drawn after compositing. This
is not impossible but for now doing it the simple way.