fix #32081 (mysqli_real_connect(): mysqli.default_socket in php.ini has no effect) for real

ext/mysqli/mysqli_api.c

@@ -1360,6 +1360,10 @@ PHP_FUNCTION(mysqli_real_connect)
 		flags ^= CLIENT_LOCAL_FILES;
 	}
 
+	if (!socket) {
+		socket = MyG(default_socket);
+	}
+
 	if (mysql_real_connect(mysql->mysql,hostname,username,passwd,dbname,port,socket,flags) == NULL) {
 		
 		php_mysqli_set_error(mysql_errno(mysql->mysql), (char *) mysql_error(mysql->mysql) TSRMLS_CC);