DOCBOOK: Element for literal "passthrough"?

Is there an appropriate element already existing in DocBook to indicate a
character which should be treated as a literal character by downstream
processors?

In essence, I need to indicate that a particular character in a
programlisting should not be replaced by a character reference, even
though it would normally be so handled.  The prototypical example is
"<"; if I use &lt; it is normally replaced in output by
a different character entity reference of the form &#nn; (where nn is
a number indicating which character).

I know how to prevent this behavior in the downstream processor (thanks
to some help from the DSSSList several months ago) via markup of the
general form  <literalchar data='&#nn;'>. An example of
use would be 

<programlisting>
while x <literalchar data='&#60;'> 5 do
  fo the bar
end
</programlisting>

which will show up in the transformed output as

while x < 5 do
  fo the bar
end

rather than 

while x &#60; 5 do
  fo the bar
end

which is what I get from the standard definition of &lt;

By extending the content model of programlisting to include literalchar,
I can use that solution directly, and it works. Since I'm already
building an extension to DocBook, this is an adequate solution.

However, I would prefer not to unnecessarily add to the DTD, to simplify
the process of adapting existing tools.  I did not find an existing
element that seemed appropriate, though, although I suppose I could abuse
literal itself.

The project is, BTW, a literate programming extension to DocBook, and
this is part of getting the "tangle" (code output) branch to
work.  So far, I have been pleasantly surprised to discover that I
can make this work with very minor changes to the standard DTD; other
than however I deal with this literal character issue, I have added three
attributes to  programlisting, and reused xreflabel.

Mark B. Wroth

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