QmlDbg: Don't wait infinitely for messages on application output

We only connect to the port when we get a 'Waiting for connection ...'
message on application output. This was done mainly to avoid lots
of failed connects, and therefore an unresponsive UI on Windows.

However, the application output might be redirected for various reasons.
Therefore fall back to busy connect after a certain time (4 seconds
for profiling, 8 seconds for debugging).

Change-Id: Ie1b943f678ced40c030cc134493a2adf7e3bc9df
Reviewed-on: http://codereview.qt.nokia.com/2323
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Christiaan Janssen <christiaan.janssen@nokia.com>

src/plugins/debugger/qml/qmlengine.h

@@ -126,6 +126,7 @@ signals:
         TextEditor::ITextEditor *editor, int cursorPos);
 
 private slots:
+    void beginConnection();
     void connectionEstablished();
     void connectionStartupFailed();
     void connectionError(QAbstractSocket::SocketError error);