The math module contains as function for floating-point numbers, as wells as functions for integer only numbers: factorial(), gcd(). Yet few integer specific functions was added in 3.8: isqrt(), perm(), comb().

The proposed PR adds the new imath module, adds into it old functions factorial() and gcd() and moves new functions. It also adds two additional functions: as_integer_ratio() and ilog2().

There are plans for adding more integer functions: divide_and_round(), is_prime(), primes(), but the work in progress.