[Bug-cpio] ustar

[Dan Jacobson]

I noticed in Info:
    `ustar'
          The POSIX.1 tar format.  Also recognizes GNU tar archives,
          which are similar but not identical.
OK, but that is good when extracting, but when creating, you've got to
tell the user how to distinguish between the two. Or say
          The POSIX.1 tar format.  Also recognizes GNU tar archives
          on extraction, which are similar but not identical.