* sysdeps/unix/sysv/linux/i386/bits/posix_opt.h: Remnove
_POSIX_THREAD_PRIORITY_SCHEDULING.
* sysdeps/unix/sysv/linux/i386/bits/posix_opt.h: Remove
_XOPEN_REALTIME_THREADS.
* sysdeps/unix/sysv/linux/bits/posix_opt.h: Likewise.
* sysdeps/unix/sysv/linux/pthread_kill.c (__pthread_kill): The
kernel returns EINVAL for PID <= 0, work around it.