Add deprecation notice about planned removal in 8.4 and advice to try using

the newer XML stuff in core.

(This should probably also be referred to in the release notes.)

contrib/xml2/README.xml2

 XML-handling functions for PostgreSQL
 =====================================
 
+    DEPRECATION NOTICE:  From PostgreSQL 8.3 on, there is XML-related
+    functionality based on the SQL/XML standard in the core server.
+    That functionality covers XML syntax checking and XPath queries,
+    which is what this module does as well, and more, but the API is
+    not at all compatible.  It is planned that this module will be
+    removed in PostgreSQL 8.4 in favor of the newer standard API, so
+    you are encouraged to try converting your applications.  If you
+    find that some of the functionality of this module is not
+    available in an adequate form with the newer API, please explain
+    your issue to pgsql-hackers@postgresql.org so that the deficiency
+    can be addressed.
+                                      -- Peter Eisentraut, 2007-05-24
+
 Development of this module was sponsored by Torchbox Ltd. (www.torchbox.com)
 It has the same BSD licence as PostgreSQL.