hgext: more patchbomb documentation + Add a description of how to enable this extension + Note which command it provides (it's not very easy to guess that "hgext.patchbomb" enables the "email" command, unless one can read Python sources) + Expand the descriptions of the -n and -m options of "hg email". + Mention that formail is (commonly) part of the procmail package.

#header#
    <title>#repo|escape#: #file|escape# history</title>
    <description>#file|escape# revision history</description>
    #entries%filelogentry#
  </channel>
</rss>