[boost] [algorithm] LSD radix sort

Dear community, I humbly offer you for perusal and review, LSD radix sort (and counting sort): https://github.com/jeremy-murphy/algorithm/tree/radix_sort The tests and docs are unfinished but the library code is as complete as I can manage without comment from others. The new files of interest are in include/boost/algorithm/integer_sort. I have more code with a speed test and CMake files in a separate repository: https://github.com/jeremy-murphy/integer-sort But perhaps I should move all those files into a branch off my Boost.Algorithm fork? Probably. Anyway, thanks in advance for any feedback and comments. Cheers. Jeremy