* Auto-pan settings currently only activate when the position of the
Overlay is set and the Overlay is already on a Map.
* The consequence of this is that creating an Overlay with position
set and then adding to a Map results in no auto-pan being performed -
it is necessary to first create the Overlay, then add to a Map and
finally set the position in order for the Map to auto-pan.
* This commit changes this behaviour so that the auto-pan settings are
also considered when the map property of the Overlay is set and not
only when the position property is set, leading to a more intuitive
behaviour.
* Fixes Issue #10843