sort_r.c Public Domain sort_r() by Isaac Turner

Imported GIT commit 7c60ef94753624291055af0b1eec291f8c4bd5a7
from https://github.com/noporpoise/sort_r
(raptor_sort_r): Added based on public domain sort_r()
(raptor_sequence_sort_r): Added based on raptor_sort_r()