SF bug #1090139: presentation typo in lib: 6.21.4.2 How callbacks are called

Doc/lib/liboptparse.tex

@@ -1249,7 +1249,7 @@ you don't need to mess around with globals or closures.  You can
 also access or modify the value(s) of any options already
 encountered on the command-line.
 \end{description}
-\item[\var{args}]
+\item[\code{args}]
 is a tuple of arbitrary positional arguments supplied via the
 \code{callback{\_}args} option attribute.
 \item[\code{kwargs}]