[Bug-cpio] Info page fix

[Dan Jacobson]

  `-A, --append'
       Append to an existing archive.  Only works in copy-out mode.  The
       archive must be a disk file specified with the -O or -F (-file)
       option.

You mean --file option, with -- not -.
By the way,

  `-F, --file=archive'
       Archive filename to use instead of standard input or output.  To

Combine this paragraph with the -O paragraph to avoid repeating. Or
note any differences.

       if you have permission to do so (typically an entry in that user's
       `~/.rhosts' file).

Is .rhosts still common?

I didn't check if the man page also has the above problems.