Rename IQ.ELEMENT to IQ.IQ_ELEMENT

to avoid confusion between the IQ element 'iq' and the IQs child
element. ELEMENT defined in an IQ sublcass should contain the *child*
element.

Add element to StreamInitation and fix FileTransferManager which still
used a packet listener instead of an IQ request handler to handle
incoming stream initiation requests.

smack-tcp/src/main/java/org/jivesoftware/smack/tcp/XMPPTCPConnection.java

@@ -948,7 +948,7 @@ public class XMPPTCPConnection extends AbstractXMPPConnection {
                         final String name = parser.getName();
                         switch (name) {
                         case Message.ELEMENT:
-                        case IQ.ELEMENT:
+                        case IQ.IQ_ELEMENT:
                         case Presence.ELEMENT:
                             try {
                                 parseAndProcessStanza(parser);