Add 64bit popcnt, make use of POPCNT instruction

By using Intel's POPCNT instruction, we can speed up popcnt by a fair amount. I have not done measurements myself, but according to benchmarks others have made, it should run at least 3 times as fast as non-sse implementations.

Furthermore, this PR will also allow to pass 64bit integers to popcnt.
runtime cost is constant time at module import. There is a good chance this codepath is useful due to someone running on Windows and compiling as 32bit application.