Update to track last chat state of a chat so that the user is not updated more than once, and the XEP is not violated.

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/trunk@6711 b35dd754-fafc-0310-a699-88a17e54d16e

source/org/jivesoftware/smack/Chat.java

@@ -169,4 +169,12 @@ public class Chat {
             listener.processMessage(this, message);
         }
     }
+
+
+    @Override
+    public boolean equals(Object obj) {
+        return obj instanceof Chat
+                && threadID.equals(((Chat)obj).getThreadID())
+                && participant.equals(((Chat)obj).getParticipant());
+    }
 }