xml: Avoid copying function name string

The function name lives for the entire request, so no need to make a
copy.

Author: ndossche

ext/xml/xml.c

@@ -1178,16 +1178,14 @@ static bool php_xml_check_string_method_arg(
 		&& parser_to_check->fcc_field.object == parser_to_check->object \
 		&& parser_to_check->fcc_field.calling_scope == NULL \
 	) { \
-		zend_string *method_name = zend_string_copy(parser_to_check->fcc_field.function_handler->common.function_name); \
+		zend_string *method_name = parser_to_check->fcc_field.function_handler->common.function_name; \
 		zend_fcc_dtor(&parser_to_check->fcc_field); \
 		bool status = php_xml_check_string_method_arg(0, new_this_obj, method_name, &parser_to_check->fcc_field); \
 		if (status == false) { \
 			zend_argument_value_error(2, "cannot safely swap to object of class %s as method \"%s\" does not exist, which was set via " handler_set_method, \
 			ZSTR_VAL(new_this_obj->ce->name), ZSTR_VAL(method_name)); \
-			zend_string_release(method_name); \
 			RETURN_THROWS(); \
 		} \
-		zend_string_release(method_name); \
 		zend_fcc_addref(&parser_to_check->fcc_field); \
 	}