Stack overflow on `pow` with mixed float and complex args

[KristofferC]

julia> NaNMath.pow(1.0, 1.0+im)
ERROR: StackOverflowError:
Stacktrace:
 [1] pow(x::ComplexF64, y::ComplexF64) (repeats 2 times)
   @ NaNMath ~/.julia/packages/NaNMath/ceWIc/src/NaNMath.jl:26

[shashi]

Also encountered this today in SymbolicUtils fuzzer.

[moble]

#79 will make it so that this no longer results in a stack overflow. It still does not treat complex arguments, but I think that's covered by #66.