HPCC-12035 Implement isnan() and isinf() for windows

Signed-off-by: Anthony Fishbeck <anthony.fishbeck@lexisnexis.com>
I've seen mention of boolean versions for c++, but the actual definitions that end up being used on linux are int.. so I modeled these after what was being used there.  I could make them bool as long as we keep the difference in mind.. although it probably wouldn't matter.