title: How can I set mapView's userLocation to a MKUserLocation that I created?
body: <p>Im trying to do some coding about improving the iPhone positioning accuracy.
  I got all needed info(e.g. latitude, longitude, deviceMotion, Gyro..) from my iPhone hardware and need to display the more accurate calculation result on the mapView.
  But just then I found that the userLocation property of the mapView is readonly, so it probably means it cannot be changed even use the setCoordinate method, so sad =[
  Is there any solution that can deal with it or there has another way to display that position on my map view?
  Thanks!</p>