vtkVRRenderWindowInteractor: Implement InternalCreateTimer/InternalDestroyTimer
vtkVRRenderWindowInteractor::InternalCreateTimer
and vtkVRRenderWindowInteractor::InternalDestroyTimer
are missing, let's implement them
vtkVRRenderWindowInteractor::InternalCreateTimer
and vtkVRRenderWindowInteractor::InternalDestroyTimer
are missing, let's implement them