title: QAction triggered signal is not passing checked parameter
body: <p>I have made a menu bar with a <code>QAction</code> which is set to checkable</p>
  
  <pre><code>self.display_features_action = QtGui.QAction("Show Features", parent)
  self.display_features_action.setCheckable(True)
  self.display_features_action.setChecked(True)
  </code></pre>
  
  <p>Then I connect to this</p>
  
  <pre><code>class MyClass:
      def __init__(....)
           ....
           self.display_features_action.triggered.connect(self.my_slot)
  
      def my_slot(self, checked)
           ....
  </code></pre>
  
  <p>But I get a runtime error that the my_slot method takes to arguments, when only one is supplied. Why isnt the checked parameter sent with the signal?</p>