[libegg] Avoid deprecated g_type_class_add_private

With minimal changes to avoid deprecated g_type_class_add_private

libegg/eggsmclient.c

@@ -48,7 +48,8 @@ struct _EggSMClientPrivate
 
 #define EGG_SM_CLIENT_GET_PRIVATE(o) (G_TYPE_INSTANCE_GET_PRIVATE ((o), EGG_TYPE_SM_CLIENT, EggSMClientPrivate))
 
-G_DEFINE_TYPE (EggSMClient, egg_sm_client, G_TYPE_OBJECT)
+G_DEFINE_TYPE_WITH_CODE (EggSMClient, egg_sm_client, G_TYPE_OBJECT,
+                         G_ADD_PRIVATE (EggSMClient))
 
 static EggSMClient *global_client;
 static EggSMClientMode global_client_mode = EGG_SM_CLIENT_MODE_NORMAL;
@@ -72,8 +73,6 @@ egg_sm_client_class_init (EggSMClientClass *klass)
 {
     GObjectClass *object_class = G_OBJECT_CLASS (klass);
 
-    g_type_class_add_private (klass, sizeof (EggSMClientPrivate));
-
     /**
      * EggSMClient::save_state:
      * @client: the client
@@ -413,7 +412,7 @@ egg_sm_client_is_resumed (EggSMClient *client)
 GKeyFile *
 egg_sm_client_get_state_file (EggSMClient *client)
 {
-    EggSMClientPrivate *priv = EGG_SM_CLIENT_GET_PRIVATE (client);
+    EggSMClientPrivate *priv = egg_sm_client_get_instance_private (client);
     char *state_file_path;
     GError *err = NULL;