Fix circular include

panda/src/display/graphicsWindowProcCallbackData.h

@@ -17,9 +17,10 @@
 
 #include "pandabase.h"
 #include "callbackData.h"
-#include "graphicsWindow.h"
 #include "touchInfo.h"
 
+class GraphicsWindow;
+
 ////////////////////////////////////////////////////////////////////
 //       Class : GraphicsWindowProcCallbackData
 // Description : This specialization on CallbackData is passed when