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/Loader/LoaderInterface.php

@@ -0,0 +1,61 @@
+<?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\Loader;
+
+use Twig\Error\LoaderError;
+
+/**
+ * Interface all loaders must implement.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ */
+interface LoaderInterface
+{
+    /**
+     * Gets the source code of a template, given its name.
+     *
+     * @param string $name The name of the template to load
+     *
+     * @return string The template source code
+     *
+     * @throws LoaderError When $name is not found
+     *
+     * @deprecated since 1.27 (to be removed in 2.0), implement Twig\Loader\SourceContextLoaderInterface
+     */
+    public function getSource($name);
+
+    /**
+     * Gets the cache key to use for the cache for a given template name.
+     *
+     * @param string $name The name of the template to load
+     *
+     * @return string The cache key
+     *
+     * @throws LoaderError When $name is not found
+     */
+    public function getCacheKey($name);
+
+    /**
+     * Returns true if the template is still fresh.
+     *
+     * @param string $name The template name
+     * @param int    $time Timestamp of the last modification time of the
+     *                     cached template
+     *
+     * @return bool true if the template is fresh, false otherwise
+     *
+     * @throws LoaderError When $name is not found
+     */
+    public function isFresh($name, $time);
+}
+
+class_alias('Twig\Loader\LoaderInterface', 'Twig_LoaderInterface');