the external general entities (files) which were getting pulled in already
contained a <programlisting/> element; this XML element was not necessary, but
the lack of an <areaspec/> inside the <programlistingco/> was giving xmllint
fits.
apparently, DocBook is quite picky about the order of children elements within
the <affiliation/> element; so rearranged; and also only one of <revremark/>
or <revdescription/> is (technically) allowed in a <revision/>, so I chose to
convert the <revremark/> elements to <remark/> and drop them inside of a
<revdescription/>, which allows much richer expression of content