Changes for 2.046 -> 2.047

Display (pop)
 * Make sure "prerequisites" like opening extern.xul dialog are complete before
   closing pop.xul
 * Avoid asking user for download folder each time, show location on main
   pop.xul dialog.

Rules
 * Support iframe method of embedding youtube videos
 * Fix vimeo.com

Overlay
 * Fix running unplug from windows without selected tab, eg: pop-out radio
   players