* thunar/thunar-preferences-dialog.c: Instead of using a transient

	  window, we do a fake-center-on-parent. So it looks like the
	  window belongs to the parent, but it is a standalone window. This
	  should fix the last part of bug #3586.
	* thunar/thunar-window.c: Register the properties dialog with
	  thunar_application_take_window() so it will get a new
	  GtkWindowGroup.

(Old svn revision: 28930)