[TASK] Reduce information disclosure of the used TYPO3 version

Reduce information disclosure of the used TYPO3 version by adding
a dynamic 4-digit year in the TYPO3_copyright_year constant.

That makes it more difficult to find out the used TYPO3 version
just by looking at the frontend source code of a website.

Releases: master, 9.5
Resolves: #87543
Change-Id: Ic169548c7111715eecedfce4ced5c8a3564d102a
Reviewed-on: https://review.typo3.org/59611
Tested-by: TYPO3com <noreply@typo3.com>
Reviewed-by: André Schließer <andy.schliesser@gmail.com>
Tested-by: André Schließer <andy.schliesser@gmail.com>
Reviewed-by: Richard Haeser <richard@maxserv.com>
Tested-by: Richard Haeser <richard@maxserv.com>
Reviewed-by: Josef Glatz <josef.glatz@typo3.org>
Tested-by: Josef Glatz <josef.glatz@typo3.org>
Reviewed-by: Oliver Klee <typo3-coding@oliverklee.de>
Reviewed-by: Andreas Wolf <andreas.wolf@typo3.org>
Tested-by: Andreas Wolf <andreas.wolf@typo3.org>

typo3/sysext/core/Classes/Core/SystemEnvironmentBuilder.php

@@ -117,7 +117,7 @@ protected static function defineBaseConstants()
         // This version, branch and copyright
         define('TYPO3_version', '9.5.5-dev');
         define('TYPO3_branch', '9.5');
-        define('TYPO3_copyright_year', '1998-2019');
+        define('TYPO3_copyright_year', '1998-' . date('Y'));
 
         // TYPO3 external links
         define('TYPO3_URL_GENERAL', 'https://typo3.org/');