title: Qt.QueuedConnection never sends message
body: <p>Why does this program not print anything?</p>
  
  <pre><code>from PyQt4.QtCore import *
  from PyQt4.QtGui import *
  
  class A(QObject):
      def __init__(self):
          super(A, self).__init__()
  
      sig = pyqtSignal()
  
      @pyqtSlot()
      def slot(self):
          print("received")
  
  a = A()
  a.sig.connect(a.slot, Qt.QueuedConnection)
  
  a.sig.emit()
  a.sig.emit()
  a.sig.emit()
  </code></pre>
  
  <p>If I remove Qt.QueuedConnection, it works as expected.  I'm trying to see if Qt.QueuedConnection will automatically remove duplicate events.</p>