Update kernel version in syscall-names.list to 4.19.

Linux 4.19 does not add any new syscalls (some existing ones are added
to more architectures); this patch updates the version number in
syscall-names.list to reflect that it's still current for 4.19.

Tested with build-many-glibcs.py.

	* sysdeps/unix/sysv/linux/syscall-names.list: Update kernel
	version to 4.19.