Fixed panning bug, when using RUN_ON_DEMAND, that resulted in the camera being thrown off towards infinity.

The solution for to refactor the way that events are checked so I add a bool return type to checkEvents() method across osgViewer::GraphcisWindow, osgGA::Devive and osgViewer::Viewer/CompositeViewer classes

include/osgViewer/api/IOS/GraphicsWindowIOS

@@ -109,7 +109,7 @@ class GraphicsWindowIOS : public osgViewer::GraphicsWindow
         virtual void swapBuffersImplementation();
         
         /** Check to see if any events have been generated.*/
-        virtual void checkEvents();
+        virtual bool checkEvents();
 
         /** Set Window decoration.*/
         virtual bool setWindowDecorationImplementation(bool flag);