Improve constant folding of noise by recognizing when noise calls
previously tagged as taking derivatives of their arguments (because they
MAY have, since it wasn't known which variety of noise it would be) are
now known not to take derivatives (because we know certainly that it's
not one of the varieties that takes derivatives). This has big implications
for reducing the cost of noise.
SIMD acceleration of 4D noise varieties

Between 3x-4x speedup, depending on exactly which varity (1D output, 3D
output, derivs or not).