Update Twig from 1.35.0 to 1.42.4 (PHP 5.5 is now required!)

This fixes some errors on PHP 7.4 and contains even more fixes
Also bumped PHP version to 5.5 as Twig requires it.

system/libs/Twig/Cache/NullCache.php

@@ -0,0 +1,42 @@
+<?php
+
+/*
+ * This file is part of Twig.
+ *
+ * (c) Fabien Potencier
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Twig\Cache;
+
+/**
+ * Implements a no-cache strategy.
+ *
+ * @final
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class NullCache implements CacheInterface
+{
+    public function generateKey($name, $className)
+    {
+        return '';
+    }
+
+    public function write($key, $content)
+    {
+    }
+
+    public function load($key)
+    {
+    }
+
+    public function getTimestamp($key)
+    {
+        return 0;
+    }
+}
+
+class_alias('Twig\Cache\NullCache', 'Twig_Cache_Null');