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/Node/Expression/Test/DefinedTest.php

@@ -0,0 +1,71 @@
+<?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\Node\Expression\Test;
+
+use Twig\Compiler;
+use Twig\Error\SyntaxError;
+use Twig\Node\Expression\ArrayExpression;
+use Twig\Node\Expression\BlockReferenceExpression;
+use Twig\Node\Expression\ConstantExpression;
+use Twig\Node\Expression\FunctionExpression;
+use Twig\Node\Expression\GetAttrExpression;
+use Twig\Node\Expression\NameExpression;
+use Twig\Node\Expression\TestExpression;
+
+/**
+ * Checks if a variable is defined in the current context.
+ *
+ *    {# defined works with variable names and variable attributes #}
+ *    {% if foo is defined %}
+ *        {# ... #}
+ *    {% endif %}
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+class DefinedTest extends TestExpression
+{
+    public function __construct(\Twig_NodeInterface $node, $name, \Twig_NodeInterface $arguments = null, $lineno)
+    {
+        if ($node instanceof NameExpression) {
+            $node->setAttribute('is_defined_test', true);
+        } elseif ($node instanceof GetAttrExpression) {
+            $node->setAttribute('is_defined_test', true);
+            $this->changeIgnoreStrictCheck($node);
+        } elseif ($node instanceof BlockReferenceExpression) {
+            $node->setAttribute('is_defined_test', true);
+        } elseif ($node instanceof FunctionExpression && 'constant' === $node->getAttribute('name')) {
+            $node->setAttribute('is_defined_test', true);
+        } elseif ($node instanceof ConstantExpression || $node instanceof ArrayExpression) {
+            $node = new ConstantExpression(true, $node->getTemplateLine());
+        } else {
+            throw new SyntaxError('The "defined" test only works with simple variables.', $lineno);
+        }
+
+        parent::__construct($node, $name, $arguments, $lineno);
+    }
+
+    protected function changeIgnoreStrictCheck(GetAttrExpression $node)
+    {
+        $node->setAttribute('ignore_strict_check', true);
+
+        if ($node->getNode('node') instanceof GetAttrExpression) {
+            $this->changeIgnoreStrictCheck($node->getNode('node'));
+        }
+    }
+
+    public function compile(Compiler $compiler)
+    {
+        $compiler->subcompile($this->getNode('node'));
+    }
+}
+
+class_alias('Twig\Node\Expression\Test\DefinedTest', 'Twig_Node_Expression_Test_Defined');