title: PySide Error emitting dataChanged signal in QAbstractItemModel subclass
body: <p>I'm getting this error when trying to emit <code>dataChanged</code> signal:</p>
  
  <pre><code>self.dataChanged.emit(index, index)
  TypeError: Value types used on meta functions (including signals) need to be registered on meta type: QModelIndex
  </code></pre>
  
  <p>Here is the relevant part of my <code>QAbstractItemModel</code> subclass:</p>
  
  <pre><code>class PropertyItemModel(QtCore.QAbstractItemModel):
      def __init__(self, parent=None):
          super(PropertyItemModel, self).__init__(parent)
  
      def setData(self, index, value, role=Qt.EditRole):
          if role != Qt.EditRole:
              return False
  
          item = self.getItem(index)
          result = item.setData(index.column(), value)
  
          if result:
              self.dataChanged.emit(index, index)
  
              # Doesn't work either (same error):
              # self.emit(QtCore.SIGNAL("dataChanged(QModelIndex, QModelIndex)"), index, index)
              # QtCore.QObject.emit(self, QtCore.SIGNAL("dataChanged(const QModelIndex&amp;, const QModelIndex&amp;)"), index, index)
  
          return result
  </code></pre>
  
  <p>I'm using PySide version 1.2.1 with Qt 4.8.5 on Mac OS X (10.10). 
  The error can be related with my specific environment. This code was working on another mac. </p>