Got the test running again! It's super-laggy, but not just a brick wall.
Turning the loading radius way down helped too of course. The terrain
is awful atm, but that'll be debugged eventually. Also there's a
segfault lurking in there somewhere, but I'm not sure exactly where.
Also also, the new 32x32 chunks were the cause of the previous error:
they were overflowing the vertex index count (32x32x36 > 2**15) because
the vertex indices were accidentally signed instead of unsigned. That's
fixed now, and 32*32*36 just barely fits into 16 bits, so everything
should be fine there.

-Peter Mawhorter