Bitcount & bitwise hamming distance

Count the set bits in vectors, and compute bitwise hamming distances between sets of vectors

This submission provides two functions:
Bitcount - Counts the number of set bits in each column of the input array, typecast as a bit vector.
Bitwise_hamming - Given two sets of bit vectors (each column being a bit vector), compute the hamming distances between all pairs of vectors between the two sets.
The latter function requires the former, but the former can also be used on its own.