Fix for bug 8237 (Prefs need to save when apprunner quits) and bug 8106

(Calling 'exit' while closing the top level window (causing the whole
app to quit).
Should let the profile manager work as advertised on unix.
Reviewed by law and mcmullen.

widget/src/gtk/nsAppShell.cpp

@@ -250,7 +250,6 @@ done:
 NS_METHOD nsAppShell::Exit()
 {
   gtk_main_quit ();
-  gtk_exit(0);
 
   return NS_OK;
 }