Numdiff 5.8.1 (new formula)

a program which compares putatively similar files line by line and field by field, ignoring small numeric differences or/and different numeric formats

IMPORTANT:
for this formula `brew audit numdiff` complains that it can't be found unless i put it into `Library/Formula` directory. So I tested that it does work from there
I think it would be better to use `ENV.append "CPPFLAGS" ...`