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/NodeVisitor/AbstractNodeVisitor.php

@@ -0,0 +1,59 @@
+<?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\NodeVisitor;
+
+use Twig\Environment;
+use Twig\Node\Node;
+
+/**
+ * Used to make node visitors compatible with Twig 1.x and 2.x.
+ *
+ * To be removed in Twig 3.1.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+abstract class AbstractNodeVisitor implements NodeVisitorInterface
+{
+    final public function enterNode(\Twig_NodeInterface $node, Environment $env)
+    {
+        if (!$node instanceof Node) {
+            throw new \LogicException(sprintf('%s only supports \Twig\Node\Node instances.', __CLASS__));
+        }
+
+        return $this->doEnterNode($node, $env);
+    }
+
+    final public function leaveNode(\Twig_NodeInterface $node, Environment $env)
+    {
+        if (!$node instanceof Node) {
+            throw new \LogicException(sprintf('%s only supports \Twig\Node\Node instances.', __CLASS__));
+        }
+
+        return $this->doLeaveNode($node, $env);
+    }
+
+    /**
+     * Called before child nodes are visited.
+     *
+     * @return Node The modified node
+     */
+    abstract protected function doEnterNode(Node $node, Environment $env);
+
+    /**
+     * Called after child nodes are visited.
+     *
+     * @return Node|false|null The modified node or null if the node must be removed
+     */
+    abstract protected function doLeaveNode(Node $node, Environment $env);
+}
+
+class_alias('Twig\NodeVisitor\AbstractNodeVisitor', 'Twig_BaseNodeVisitor');