Allows non-dragging pans that are initiated on views to pan the underlying map.
Annotation views each have long press and pan gesture recognizers. If a
view is not draggable or not in a positive dragging state, the pan
gesture recognizer should not begin. This commit makes the criteria for
rejecting pans more strict — only `_panGestureRecognizer` should be
rejected, not the entire `UIPanGestureRecognizer` class.
bc845b96b0