Use short names for some locales
As in Firefox itself, see ftp://ftp.mozilla.org/pub/mozilla.org/firefox/releases/19.0/win32/xpi/
Fix saveURL(): pass source document for new Firefox versions
(per-window private browsing)
install.js aren't needed:
https://developer.mozilla.org/en-US/docs/XUL/Tutorial/Install_Scripts
Use <menupopup> instead of <popup>