Update syscall-names.list for Linux 5.1.

Update syscall-names.list for Linux 5.1.

This patch updates syscall-names.list for Linux 5.1 (which has many
new syscalls, mainly but not entirely ones for 64-bit time).

Tested with build-many-glibcs.py (before the revert of the move to
Linux 5.1 there; verified there were no tst-syscall-list failures).

	* sysdeps/unix/sysv/linux/syscall-names.list: Update kernel
	version to 5.1.
	(clock_adjtime64) New syscall.
	(clock_getres_time64) Likewise.
	(clock_gettime64) Likewise.
	(clock_nanosleep_time64) Likewise.
	(clock_settime64) Likewise.
	(futex_time64) Likewise.
	(io_pgetevents_time64) Likewise.
	(io_uring_enter) Likewise.
	(io_uring_register) Likewise.
	(io_uring_setup) Likewise.
	(mq_timedreceive_time64) Likewise.
	(mq_timedsend_time64) Likewise.
	(pidfd_send_signal) Likewise.
	(ppoll_time64) Likewise.
	(pselect6_time64) Likewise.
	(recvmmsg_time64) Likewise.
	(rt_sigtimedwait_time64) Likewise.
	(sched_rr_get_interval_time64) Likewise.
	(semtimedop_time64) Likewise.
	(timer_gettime64) Likewise.
	(timer_settime64) Likewise.
	(timerfd_gettime64) Likewise.
	(timerfd_settime64) Likewise.
	(utimensat_time64) Likewise.