Update CodeIgniter.php

Fixed :

When I touch /alidata/www/app/config/development/ and edit index.php define('ENVIRONMENT', 'development');

Warning: require_once(/alidata/www/app/config/constants.php): failed to open stream: No such file or directory in /alidata/www/ci3/core/CodeIgniter.php on line 70

Fatal error: require_once(): Failed opening required '/alidata/www/app/config/constants.php' (include_path='.:/alidata/server/php/lib/php') in /alidata/www/ci3/core/CodeIgniter.php on line 70