Name all timeouts and idles

Better names can be used once we make more use of them.

https://bugzilla.gnome.org/show_bug.cgi?id=727979

src/backends/meta-monitor-manager.c

@@ -931,6 +931,7 @@ meta_monitor_manager_handle_apply_configuration  (MetaDBusDisplayConfig *skeleto
   if (persistent)
     {
       manager->persistent_timeout_id = g_timeout_add_seconds (20, save_config_timeout, manager);
+      g_source_set_name_by_id (manager->persistent_timeout_id, "[mutter] save_config_timeout");
       g_signal_emit (manager, signals[CONFIRM_DISPLAY_CHANGE], 0);
     }