Blender Git Loki

Fix T54190: Occlusion query select failed

By default select wasn't picking the nearest object,
this could have been fixed by not clearing the depth buffer,
but calling GPU_select_(begin/end) without the binded frame-buffer
caused issues for depth-picking. So move GPU_select begin/end to a
callback.

This also has the advantage that only needs to populate the engines once
to draw two passes.

Note that cycling through objects fails with occlusion queries still,
will fix shortly.