The info isn't used yet, but this shows that vulkan's occlusion queries
are at least somewhat useful. However, the technique isn't perfect:
infinite radius lights (1/r and 1/r^2) are difficult to cull, and all
lights can poke through thin enough walls, and then lights containing
the camera get culled incorrectly (will need a separate test). Still, it
looks like it will help once everything is tied together.
I really don't know what I was thinking when I wrote that code. Maybe I
was trying for a half angle. Now the rendered "cone" matches up with a
hard-clipped cone light (soft edges stick out a bit).
