have docbook generate valid html

have docbook generate valid html

http://validator.w3.org/check
fusses about 'end tag for element "P" which is not open'
if a table is inside a paragraph - eg
  <p><table> ... </table></p>

docbook 3.1 turns <screen> and <programlisting> into
html <table>s, so get rid of all the enclosing <para>s

problematic constructs:
<para><figure> ... </figure></para>
<para><itemizedlist> ... </itemizedlist></para>
<para><literal> ... </literal></para>
<para><orderedlist> ... </orderedlist></para>
<para><programlisting> ... </programlisting></para>
<para><screen> ... </screen></para>
<para><simplelist> ... </simplelist></para>