Avoid concurrent directory writes in FilesystemIterator test

The test directory is often used for temporary files, let's use
the source directory, which should be more stable. If that doesn't
work we need to create a temporary directory.

Author: nikic

ext/spl/tests/dit_005.phpt

@@ -2,7 +2,8 @@
 SPL: FilesystemIterator and clone
 --FILE--
 <?php
-$a = new FileSystemIterator(__DIR__);
+// Let's hope nobody writes into this directory while testing...
+$a = new FileSystemIterator(__DIR__ . '/..');
 $b = clone $a;
 var_dump((string)$b == (string)$a);
 var_dump($a->key() == $b->key());