When loading a new url into an existing view, don't update the location bar immediately, but when starting to load it into the view for real. This fixes:
- click on link which opens in new app: the url was shown temporarily and then reverted
- constant redirects would keep updating the location bar url, masking the current url
But we still show the url immediately when loading a url into a new window or tab, for early user feedback.

Also fixed double-part-activation bug which was clearing up the url temporarily during startup (and slowing down startup, too, since AFAICS it was doing xmlgui-building twice for KHTML).