qsort() isn't thread safe

Issue

• In RHEL5, a multi-threaded application using the qsort() function may dump core with a floating point exception. We found out that RHEL6 has the same problem.
• The qsort() function is not listed as "need not be thread-safe" functions in POSIX.1-2008, "2.9.1 Thread-Safety". So it shall be thread-safe and be safely available in the multi-threaded application.
• This problem is already fixed in the latest upstream glibc(<= 2.12.2).
  http://sourceware.org/bugzilla/show_bug.cgi?id=11655