* include/stdlib.h: Add hidden_proto for qsort_t and adjust protoype
for _quicksort.
* stdlib/msort.c (qsort): Now a wrapper around qsort_r.
(qsort_r): Renamed from qsort. Take additional parameter and pass it
on as third parameter to compare function and _quicksort.
* stdlib/qsort.c (_quicksort): Take additional parameter and pass on
to the compare function.
* stdlib/Versions [libc] (GLIBC_2.8): Add qsort_r.
* Versions.def: Add GLIBC_2.8 for libc.