callout-lists and HTML/PDF creation with xsltproc/libxslt

Hello,

When I try to process a <screenco> or <programlistingco> element with
xsltproc to output HTML, it works, except that the numbers in the
<screen> or <programlisting> area are missing [1]. If I now try to
create FO output using the docbook-xsl stylesheets and xsltproc, it
fails. Are the FO-stylesheets only behind the HTML stylesheets or are
there problems with callouts for FO-output, that cannot be solved
without a special extension?

My problem is, that I would like to comment some screen-output, but the
linenumbering attribute needs an extension, libxslt does not provide,
and the PDF output seems to fail for callouts and shows the explained
problem for HTML. But I cannot use Saxon or Xalan, because Xerces seems
to miss support for xpointer(), which I need for some includes (system
is a Debian Sid).

[1] If I process the docbook-defguide with xsltproc, it produces the
correct output for the screenco-example - if I process the
screenco/example1.xml alone, it shows the same problem - the numbers are
missing in the <screen>-area.

Regards, Daniel