⬆️ Upgrade lib : nikic/php-parser

We were on v3 that is no longer maintained and compatibility is annonced for PHP 7.2.
v4 is active and supports PHP up to 8.0
No problem to update as this is only used in the config editor (\Combodo\iTop\Config\Validator\iTopConfigAstValidator)

lib/nikic/php-parser/lib/PhpParser/Internal/DiffElem.php

@@ -0,0 +1,27 @@
+<?php declare(strict_types=1);
+
+namespace PhpParser\Internal;
+
+/**
+ * @internal
+ */
+class DiffElem
+{
+    const TYPE_KEEP = 0;
+    const TYPE_REMOVE = 1;
+    const TYPE_ADD = 2;
+    const TYPE_REPLACE = 3;
+
+    /** @var int One of the TYPE_* constants */
+    public $type;
+    /** @var mixed Is null for add operations */
+    public $old;
+    /** @var mixed Is null for remove operations */
+    public $new;
+
+    public function __construct(int $type, $old, $new) {
+        $this->type = $type;
+        $this->old = $old;
+        $this->new = $new;
+    }
+}