Cycles: Use more accurate implementation of erf() and erfinv()
Cycles: Use more accurate implementation of erf() and erfinv()

This functions are  orders of magnitude more accurate than the old ones,
and they're around the same complexity to compute.

pyrochlore/cycles,tangent-opensource/coreBlackbird,pyrochlore/cycles,tangent-opensource/coreBlackbird,pyrochlore/cycles,tangent-opensource/coreBlackbird