Adding back isJoined method, which got deleted somehow...

git-svn-id: http://svn.igniterealtime.org/svn/repos/smack/trunk@2107 b35dd754-fafc-0310-a699-88a17e54d16e

source/org/jivesoftware/smack/GroupChat.java

@@ -198,6 +198,16 @@ public class GroupChat {
         joined = true;
     }
 
+    /**
+     * Returns true if currently in the group chat (after calling the {@link
+     * #join(String)} method.
+     *
+     * @return true if currently in the group chat room.
+     */
+    public boolean isJoined() {
+        return joined;
+    }
+
     /**
      * Leave the chat room.
      */