This PR adds support for lowering the following Math operations to
`libm` calls:
* `math.absf` -> `fabsf, fabs`
* `math.exp` -> `expf, exp`
* `math.exp2` -> `exp2f, exp2`
* `math.fma` -> `fmaf, fma`
* `math.log` -> `logf, log`
* `math.log2` -> `log2f, log2`
* `math.log10` -> `log10f, log10`
* `math.powf` -> `powf, pow`
* `math.sqrt` -> `sqrtf, sqrt`
These operations are direct members of `libm`, and do not seem to
require any special manipulations on their operands.
50b937331f