Add reference to the "String Methods" section to make that information

easier to find.  Based on the comment from Steve Alexander on the
zope-coders mailing list.

Doc/lib/libstrings.tex

@@ -5,3 +5,6 @@ The modules described in this chapter provide a wide range of string
 manipulation operations.  Here's an overview:
 
 \localmoduletable
+
+Information on the methods of string objects can be found in
+section~\ref{string-methods}, ``String Methods.''