stdlib: Add more qsort{_r} coverage

This patch adds a qsort and qsort_r to trigger the worst case
scenario for the quicksort (which glibc current lacks coverage).
The test is done with random input, dfferent internal types (uint8_t,
uint16_t, uint32_t, uint64_t, large size), and with
different set of element numbers.

Checked on x86_64-linux-gnu and i686-linux-gnu.
Reviewed-by: Noah Goldstein <goldstein.w.n@gmail.com>