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/Twig/CompilerInterface.php

@@ -0,0 +1,34 @@
+<?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.
+ */
+
+/**
+ * Interface implemented by compiler classes.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @deprecated since 1.12 (to be removed in 3.0)
+ */
+interface Twig_CompilerInterface
+{
+    /**
+     * Compiles a node.
+     *
+     * @return $this
+     */
+    public function compile(Twig_NodeInterface $node);
+
+    /**
+     * Gets the current PHP code after compilation.
+     *
+     * @return string The PHP code
+     */
+    public function getSource();
+}