When shade.verbatim is turned on for HTML output,
then a programlistingco with callouts is mishandled. For
each callout, the table used to create the background
shading is terminated, the callout bug is output, and a
new table is started.
This seems to be a bug in the Saxon XSLT extension
that handles callouts.
The attached xml file illustrates the problem when it is
processed to HTML with shade.verbatim on (using