optimize python-mode square root: avoid call to bitcount(); use division in isqrt_fast up to a higher limit
optimize python-mode square root: avoid call to bitcount(); use division in isqrt_fast up to a higher limit

JensGrabner/mpmath,JensGrabner/mpmath,klkuhlm/mpmath,bjodah/mpmath,bjodah/mpmath,klkuhlm/mpmath,fredrik-johansson/mpmath