title: How can I detect when the user taps on the currently selected pin on MKMapView?
body: <p>MKMapView provides the didSelectAnnotationView: method to report when the user first taps a pin.  The result of this is that the map callout gets displayed.  I need to let the user dismiss the map callout by tapping the pin a second time.  </p>
  
  <p>Unfortunately, the didSelectAnnotationView: method does not fire when the user taps a pin which is already selected.</p>