MGLMapView observes changes to the coordinate property of each MGLAnnotation added to it. Changing the coordinate property in a KVO-compliant way causes the annotation to be relocated and its callout view, if present, to be dismissed. To avoid observing the same annotation twice yet also avoid expensive lookups when adding or removing annotations, MGLMapView indexes added point annotations in an NSMutableSet.
In iosapp, tapping a callout view moves the selected annotation to the center of the screen and deselects it.
Fixes#1980.
8a4c2d4b0e
