config: add handler for SIGHUP and a reload-configuration stub

src/main-utils.h

@@ -37,4 +37,9 @@ gboolean nm_main_utils_early_setup (const char *progname,
                                     gpointer option_context_hook_data,
                                     const char *summary);
 
+/* The following functions are not implemented inside nm-main-utils.c, instead
+ * main.c and nm-iface-helper.c */
+
+void nm_main_config_reload (void);
+
 #endif /* __MAIN_UTILS_H__ */