Add documentation for SGMLParser.handle_decl().
diff --git a/Doc/lib/libsgmllib.tex b/Doc/lib/libsgmllib.tex
index 9907caa..5fe0c8d 100644
--- a/Doc/lib/libsgmllib.tex
+++ b/Doc/lib/libsgmllib.tex
@@ -145,6 +145,16 @@
default method does nothing.
\end{methoddesc}
+\begin{methoddesc}{handle_decl}{data}
+Method called when an SGML declaration is read by the parser. In
+practice, the \code{DOCTYPE} declaration is the only thing observed in
+HTML, but the parser does not discriminate among different (or broken)
+declarations. Internal subsets in a \code{DOCTYPE} declaration are
+not supported. The \var{data} parameter will be the entire contents
+of the declaration inside the \code{<!}...\code{>} markup. The
+default implementation does nothing.
+\end{methoddesc}
+
\begin{methoddesc}{report_unbalanced}{tag}
This method is called when an end tag is found which does not
correspond to any open element.