Added a jobs system, and made a job in worldgen that generates (and
throws away, for now) a column of chunks. Yet to be tested, but it
compiles, even with typedefing function pointer types that return void
function pointers!

-Peter Mawhorter
Added some testing code; in particular noise profiling code to time
calls to sxnoise_2d.

-Peter Mawhorter
Did some optimization that has chunk generation running in realish?
time. Unfortunately now the program quickly blows up either graphics
memory or the heap, I'm not sure which, despite no changes (I thought)
on the memory front.

-Peter Mawhorter