fix a off by one error in calculating k (thanks to tip from Tobias Kalbitz)
use uint for size, width and height
Merge remote-tracking branch 'm42a/c++optimizations'

Conflicts:
	ref/rays.cpp
go back to int
ignore crays
allow control of number of threads from command line
go: only negate the coordinates once (thanks to tip from Marc Aldorasi)
optimize the orig object addition
go: move the subtraction inside
go: lazy compute bounce vector
go: compute sf smartly
go: make parallel rendering more optimal
go: -procs only controls the number of render goroutines
go: allow rnd to be inlined
go: go back to old style concurrency