It now uses the ring buffer code I wrote for qwaq (and forgot about,
oops) to handle the packets themselves, and the logic for allocating and
freeing space from the buffer is a bit simpler and seems to be more
reliable. The automated test is a bit of a joke now, though, but coming
up with good tests for it... However, nq now cycles through the demos
without obvious issue under the same conditions that caused the light
map update code to segfault.
