[TASK] Change check for TYPO3_MODE

Change check for TYPO3_MODE:

if (!defined('TYPO3_MODE')) {
	die('Access denied.');
}

to

defined('TYPO3_MODE') or die();

Releases: 2.0.0
Change-Id: Iad1d55bb7c0cee388c63a6fee6524b82298afee3
Reviewed-on: https://review.typo3.org/31466
Reviewed-by: Wouter Wolters
Tested-by: Wouter Wolters