title: Track MKMapView rotation
body: <p>I have a MapKitView which has annotation which point in a certain direction. My problem is that when the user rotates the map using two fingers, or if the map rotates to track the user's heading, my symbol need to be rotated (which they don't as they are screen aligned).</p>
  
  <p>I know I can rotate the symbols by the opposite of the map camera heading.
  I know I can be notified of changes in the user's heading to rotate the annotation in that case.</p>
  
  <p>My problem is that I can't find a way of tracking the rotation of the map due to the user rotating it interactively.</p>
  
  <p>I can track start and end of map region changes, but not the changes between the two.
  I tried using KVO with the camera's bearing but I'm not getting anything.
  I tried looking for notifications sent by the system, but again, nothing.</p>
  
  <p>Anyone have any suggestions on how to reliably track the current map rotation?</p>