avoid double events when using the info button (mouse down and up)

Core/Core.cc

@@ -777,6 +777,7 @@ Core::slotMouseEventIdentify( QMouseEvent* _event )
 
   // Only catch left-button clicks
   if(_event->button() != Qt::LeftButton) return;
+  if(_event->type() != QEvent::MouseButtonRelease) return;
 
   const QObject* senderPointer = sender();
   unsigned int examinerId = 0;