libnm-glib: add class padding for future expansion

libnm-glib/nm-settings-interface.h

@@ -77,6 +77,14 @@ struct _NMSettingsInterface {
 	                        NMSettingsConnectionInterface *connection);
 
 	void (*connections_read) (NMSettingsInterface *settings);
+
+	/* Padding for future expansion */
+	void (*_reserved1) (void);
+	void (*_reserved2) (void);
+	void (*_reserved3) (void);
+	void (*_reserved4) (void);
+	void (*_reserved5) (void);
+	void (*_reserved6) (void);
 };
 
 GType nm_settings_interface_get_type (void);