Tell user why we exit() the browser
Torbrowser currently quits silently when it's not finding the preference "torbrowser.version". This can be very confusing for the end user and cause him to debug at the wrong ends, because he has no idea what's wrong. The browser should instead show a dialog with an error message, and then quit.
This is trivial to implement: Just add an alert("Error: Not started from Vidalia. Exiting"); before the quit(3);