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/SourceContextLoaderInterface.php

@@ -0,0 +1,38 @@
+<?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;
+use Twig\Source;
+
+/**
+ * Adds a getSourceContext() method for loaders.
+ *
+ * @author Fabien Potencier <fabien@symfony.com>
+ *
+ * @deprecated since 1.27 (to be removed in 3.0)
+ */
+interface SourceContextLoaderInterface
+{
+    /**
+     * Returns the source context for a given template logical name.
+     *
+     * @param string $name The template logical name
+     *
+     * @return Source
+     *
+     * @throws LoaderError When $name is not found
+     */
+    public function getSourceContext($name);
+}
+
+class_alias('Twig\Loader\SourceContextLoaderInterface', 'Twig_SourceContextLoaderInterface');