make sure dom extension is present

ext/reflection/tests/reflectionExtension_getDependencies_basic.phpt

@@ -2,6 +2,10 @@
 ReflectionExtension::getDependencies() method on an extension with a required and conflicting dependency
 --CREDITS--
 Felix De Vliegher <felix.devliegher@gmail.com>
+--SKIPIF--
+<?php
+if (!extension_loaded("dom")) die("skip no dom extension");
+?>
 --FILE--
 <?php
 $dom = new ReflectionExtension('dom');