title: UIDevice currentDevice's "orientation" always null
body: <p>As per the title. 
  Calling [[UIDevice currentDevice] BeginGeneratingDeviceOrientationNotifications] has no effect.</p>
  
  <p>DidRotateToInterfaceOrientation etc events are working fine, but I need to be able to poll the device orientation arbitrarily.</p>
  
  <p>How can I fix/do this?</p>
  
  <p>The long story:
  I have a tab application with a navigation controller on each tab. The root view of tab number one is a graph that goes full screen when the orientation changes to landscape; however this needs to be checked whenever the view appears as the orientation change could have occurred elsewhere, so I was hoping to poll the orientation state whenever this view appears.</p>