Reducing comparisons (at the cost of some speed)

Work-in-progress version of the algorithm after switching from linear searches to binary or hybrid searches in a few places. It now always uses fewer comparisons than __inplace_stable_sort() in the available test cases, and it's still always at least 2.5x faster, but compared to the previous version of WikiSort it's about 10% slower.

Most of the slowdown is due to using a binary-search variant of insertion sort to reduce the number of comparisons, apparently from the added computation complexity and nonlinear memory accesses.