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/ExistsLoaderInterface.php

@@ -0,0 +1,33 @@
+<?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;
+
+/**
+ * Adds an exists() method for loaders.
+ *
+ * @author Florin Patan <florinpatan@gmail.com>
+ *
+ * @deprecated since 1.12 (to be removed in 3.0)
+ */
+interface ExistsLoaderInterface
+{
+    /**
+     * Check if we have the source code of a template, given its name.
+     *
+     * @param string $name The name of the template to check if we can load
+     *
+     * @return bool If the template source code is handled by this loader or not
+     */
+    public function exists($name);
+}
+
+class_alias('Twig\Loader\ExistsLoaderInterface', 'Twig_ExistsLoaderInterface');