Here's a summary of what was done here:
 - remove configure checks for libgnome and libgnomeui
 - add a copy of EggSMClient (and add configure checks for sm & ice)
 - patch the copy of EggSMClient to add egg_sm_client_startup. See
   https://bugzilla.gnome.org/show_bug.cgi?id=606786 for details
 - convert the GnomeClient code we were using to use EggSMClient
 - use egg_set_desktop_file(), so we don't have to manually set the
   application name and default window icon
 - replace GnomeProgam usage with GOption and gtk_init()
 - remove the gnome_disable_sound_events workaround in PanelToplevel
   (that was disabling libgnomeui sounds for those widgets)

Note that we apparently don't need to call bonobo_init(), so we don't
call it for now.