add new test

ext/spl/tests/dit_001.phpt

@@ -0,0 +1,11 @@
+--TEST--
+SPL: Problem with casting to string
+--FILE--
+<?php
+$d = new DirectoryIterator('.');
+preg_match('/x/', $d);
+var_dump($d);
+?>
+--EXPECTF--
+object(DirectoryIterator)#%d (0) {
+}