attempt to properly check if we can use CPU_SET with sched_setaffinity because some older libc had gnu extensions in the definitions of CPU_SET which we do not allow (FSBUILD-226)

git-svn-id: http://svn.freeswitch.org/svn/freeswitch/trunk@16263 d0543943-73ff-0310-b7d9-9358b9ac24b2