minor #2493 Update .php_cs.dist (SpacePossum)

This PR was merged into the 1.x branch.

Discussion
----------

Update .php_cs.dist

following https://github.com/twigphp/Twig/pull/2490#discussion_r119097107
:)

Commits
-------

8539a18f Update .php_cs.dist

.php_cs.dist

@@ -9,6 +9,7 @@ return PhpCsFixer\Config::create()
         'no_unreachable_default_argument_value' => false,
         'braces' => array('allow_single_line_closure' => true),
         'heredoc_to_nowdoc' => false,
+        'dir_constant' => false,
     ))
     ->setRiskyAllowed(true)
     ->setFinder(PhpCsFixer\Finder::create()->in(__DIR__))