Push xmllib to the end of the markup chapter since it is deprecated.

Doc/lib/lib.tex

@@ -233,9 +233,9 @@ and how to embed it in other applications.
 \input{markup}                  % Structured Markup Processing Tools
 \input{libsgmllib}
 \input{libhtmllib}
-\input{libxmllib}
 \input{libpyexpat}
 \input{xmlsax}
+\input{libxmllib}
 
 \input{libmm}			% Multimedia Services
 \input{libaudioop}