Use of localtimestamp can be misleading

[gravitystorm]

https://github.com/zerebubuth/openstreetmap-watch-list/blob/master/cpp/src/osm/db/owl_database.cpp#L308

When updating, the current timestamp is used as the time attribute of the change. But when OWL is lagging behind, this can cause confusion - e.g. showing something as "3 hours ago" when the change itself is a week old.

It would be better to use the timestamp from the element in the change file instead.