use NULL to load plugins from default plugin directory

src/libstrongswan/plugins/plugin_loader.c

@@ -116,6 +116,11 @@ static bool load(private_plugin_loader_t *this, char *path, char *list)
 	char *token;
 	bool critical_failed = FALSE;
 
+	if (path == NULL)
+	{
+		path = PLUGINDIR;
+	}
+
 	enumerator = enumerator_create_token(list, " ", " ");
 	while (!critical_failed && enumerator->enumerate(enumerator, &token))
 	{

src/libstrongswan/plugins/plugin_loader.h

@@ -37,7 +37,7 @@ struct plugin_loader_t {
 	 * as a critical plugin. If loading a critical plugin fails, plugin loading
 	 * is aborted and FALSE is returned.
 	 *
-	 * @param path			path containing loadable plugins
+	 * @param path			path containing loadable plugins, NULL for default
 	 * @param list			space separated list of plugins to load
 	 * @return				TRUE if all critical plugins loaded successfully
 	 */