Add capability for MIX in client's server;

xep-0369.xml

@@ -52,6 +52,7 @@
       rename jidmap2 to jidmap-visible;
       Namespace bump to mix:1;
       Correct from in response of join/leave IQs;
+      Add capability for MIX in client's server;
     </p></remark>
   </revision>
   <revision>
@@ -2487,6 +2488,29 @@ This approach  enables flexible support of multiple clients for a MIX channel pa
   </section2>
 
 
+  <section2 topic="Client Determines MIX Capability of Local Server" anchor="user-server-client-capability">
+    <p>
+      Servers supporting the capabilities necessary to enable MIX clients MUST advertise this.   A client wishing to use MIX MUST check for this capability in the server before using MIX.  The capability is represented by the 'urn:xmpp:mix:account:0' feature.
+    </p>
+    <example caption="Client Determines MIX Capability of Local Server"><![CDATA[
+<iq from='hag66@shakespeare.example/UUID-c8y/1573'
+    id='lx09df27'
+    type='get'>
+  <query xmlns='http://jabber.org/protocol/disco#info'/>
+</iq>
+
+<iq from='shakespeare.example'
+    id='lx09df27'
+    to='hag66@shakespeare.example/UUID-c8y/1573'
+    type='result'>
+  <query xmlns='http://jabber.org/protocol/disco#info'>
+    <feature var='urn:xmpp:mix:account:0'/>
+  </query>
+</iq>
+]]></example>
+    
+  </section2>
+#
   <section2 topic="MIX Management and Discovery" anchor="user-server-disco">
     <p>
       Most interaction between  a MIX client and a MIX channel is directly between the client and the channel. The participant's server relays the message but does not modify the messages.   In particular configuration management and discovery is direct.   Interaction will be direct, unless explicitly stated otherwise.