The code dealing with state is a bit of a mess, but everything is
working nicely. Get around 400fps when all 6 faces need to be rendered
(no surprise: it should be about 1/6 of that for normal rendering). The
messy state handling code did not come as a surprise as I suspected
there were various mistakes in my scene rendering "recipe", and fisheye
highlighted them nicely (I'm sure getting this stuff working in Vulkan
will highlight even more issues).
