Convert things that look like man page references (i.e.,
command(number)) from the variety of different existing markup
(which included <command>, <emphasis>, and <ulink>s to man2html
CGI scripts) to a common format, which is

<citerefentry>
  <refentrytitle>command</refentrytitle>
  <manvolnum>number</manvolnum>
</citerefentry>

although in the interests of keeping the changes as simple as possible
for the translators, the above was flattened on to one line.