Example of an asciidoc link anchor failing to work depending on the
immediately following content. When 'make' runs, the document is run
through a2x twice. The first time the 'inctext' attribute is defined,
the second time not.

When 'inctext' is not defined, a [source] directive immediately follows
the 'submit' anchor in the text. xmllint fails to validate
the intermediate test.xml, with an error like:

fails/test.xml:18: element xref: validity error : IDREF attribute linkend references an unknown ID "submit"

If XMLLINT is defined to --no-xmllint, xsltproc is run and generates a
bad link to '???' in the generated fails/test.html (as would be
expected).

When 'inctext' is defined, a sentence of random text is included
immediately after the 'submit' anchor in the text and prior to the
[source] directive. Xrefs to that anchor succeed, coming out as 'submit'
in the generated works/test.html.

Comparing the intermediate docbook shows:

$ diff works/test.xml fails/test.xml
23d22
< <simpara id="submit" xreflabel="submit">If this sentence is commented out, the anchor fails to work when using a2x (but not when using asciidoc).</simpara>

The first asciidoc step is not generating 'id' and 'xreflabel' attribute
on the Docbook <programlisting> corresponding to the [source] directive
in test.txt, even though those attributes are supported (and if manually
added and the result run through xsltproc, do the right thing).
