 * run SmDiscardCommand when necessary (e.g. pending clients do not fire up,
   or we reach another checkpoint/shutdown)
 * Honor SmRestartStyleHint
 * Add APM support (separate SM client)
 * Add an option to disable Autostart by xfce4-session
 * Add configure options to make packagers life easier regarding the
   "shutdown/reboot" thing (see the Mail from Marcel Pol on 20031120)
   [partly done]
