Boost C++ Libraries

Making a radix sort stable requires the usage of an external copy of the data. A stable hybrid algorithm also requires a stable comparison-based algorithm, and these are generally slow. LSD radix sort uses an external copy of the data, and provides stability, along with likely being faster (than a stable hybrid sort), so that's probably a better way to go for integer and floating-point types. It might make sense to make a stable version of string_sort using external memory, but for simplicity this has been left out for now.