[fluxus] commits

[dave]

* Fixed some really rare garbage collection crashes. It took several
days to find a repeatable case and eventually fix it, I'll do some
overnight soak tests next.
* Documentation tweaks, typos etc
* Made the NURBS primitives constant time - rather than dynamically
tesselating and slowing down occasionally. This makes them much better
for live use.
* A check for (grab 0)
* (clear) unlocks the camera

cheers,

dave