xfs_io: implement 'utimes' command

xfs_io: implement 'utimes' command

Add the utimes command to provide a way to utilize
the futimens C library call. This is the
interface to the utimensat system call, which updates
the mtime and atime of a file.

[ sandeen: minor merge fixups, re-alphabetization ]

Signed-off-by: Deepa Dinamani <deepa.kernel@gmail.com>
Reviewed-by: Eric Sandeen <sandeen@redhat.com>
Signed-off-by: Eric Sandeen <sandeen@sandeen.net>