Match target set of ops generated by Halide about cgramapper

[rdaly525]

@jeffsetter Can you provide me a comprehensive list of all the halide ops used for our apps?

[jeffsetter]

This list expands upon the operators already existing as the core primitives in CoreIR.

Mapper should also expect to efficiently map the following from Halide (mostly originating from commonlib.cpp):
comparisons (< > <= >= == !=)
min, max, clamp
abs, absd
div, mad
exp, pow, accum
atan2

Note that many other operators are possible from Halide, as listed in IROperator.h
However, sinusoids and other functions do not have a clear use so far.

[mahorowitz]

Someone should talk with Nikhil, since I think he has efficient implementations of these type of library functions