Document that Kerberos is for authentication, and does not encrypt data

or queries over the network.

doc/src/sgml/client-auth.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/client-auth.sgml,v 1.95 2006/11/17 23:25:17 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/client-auth.sgml,v 1.96 2006/11/23 05:39:17 momjian Exp $ -->
 
 <chapter id="client-authentication">
  <title>Client Authentication</title>
@@ -653,6 +653,9 @@ local   db1,db2,@demodbs  all                         md5
     <ulink url="http://web.mit.edu/kerberos/www/">MIT Kerberos page</ulink>
     can be good starting points for exploration.
     Several sources for <productname>Kerberos</> distributions exist.
+    <productname>Kerberos</productname> provides secure authentication but
+    does not encrypt queries or data passed over the network;  for that
+    use <acronym>SSL</acronym>.
    </para>
 
    <para>