It turns out bsp faces are still back-face culled despite the null point
being on the front of every possible plane... or really, because it's on
the front of every possible plane: sometimes the back face is the front
face, and this breaks the face selection code (a separate traversal
function will be needed for non-culling rendering).
Despite that, other than having to deal with different pipelines,
getting the model renderers working went better than expected.
This gets the shaders needed for creating shadow maps, and the changes
to the lighting pipeline for binding the shadow maps, but no generation
or reading is done yet. It feels like parts of various systems are
getting a little big for their britches and I need to do an audit of
various things.
