Add math.erf lowering to libm call. Add math.erf polynomial approximation. Reviewed By: silvas, ezhulenev Differential Revision: https://reviews.llvm.org/D112200
Differential Revision: https://reviews.llvm.org/D96704
This does not split transformations, yet. Those will be done as future clean ups. Differential Revision: https://reviews.llvm.org/D96272