A few codepaths had to rely on a global variable when sorting
elements of an array because sort(3) API does not allow extra data
to be passed to the comparison function. Use qsort_s() when
natively available, and a fallback implementation of it when not,
to eliminate the need, which is a prerequisite for making the
codepath reentrant.
* rs/qsort-s:
ref-filter: use QSORT_S in ref_array_sort()
string-list: use QSORT_S in string_list_sort()
perf: add basic sort performance test
add QSORT_S
compat: add qsort_s()
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