nd as a performance enhancement.  However, if you
    perform any custom post-processing on archives that depends on
    the old numeric-style format, you will need to take this change
    into account.  </p>

<h3><a name="mhonarc::write_attachment"><tt>mhonarc::write_attachment</tt>: API change</a></h3>
    <p><tt>mhonarc::write_attachment</tt> is the main routine for
    <a href="resources/mimefilters.html">filters</a> that save data to
    an external file.  The signature of the routine was changed while