i3bar: inform _all_ clients of new tray selection owner

This fixes a problem with X-chat (and possibly others).

Fixes: #745

i3bar/src/xcb.c

@@ -1042,7 +1042,7 @@ void init_tray() {
     xcb_send_event(xcb_connection,
                    0,
                    xcb_root,
-                   XCB_EVENT_MASK_STRUCTURE_NOTIFY,
+                   0xFFFFFF,
                    (char*)ev);
     free(event);
     free(tray_reply);