Description:
------------
Due to this bug I cannot use PHP AppendIterator because it gives wrong (doubled) results. It is very hard to explain it, so there is isolated use case http://davidgrudl.com/tmp/appenditerator.zip

It affects all PHP versions.

Test script:
---------------
/*
Directory structure:

	/one
		a
		/b
			c
			d

	/two
*/


class Filter extends FilterIterator
{
	public function accept()
	{
		$this->x++;
		return $this->x > 1;
	}
}


$append = new AppendIterator();
$iterator = new RecursiveDirectoryIterator('one', RecursiveDirectoryIterator::SKIP_DOTS);
$iterator = new RecursiveIteratorIterator($iterator);
$iterator = new Filter($iterator);
$append->append($iterator);

$iterator = new RecursiveDirectoryIterator('two');
$iterator = new RecursiveIteratorIterator($iterator);
$append->append($iterator);

foreach($append as $file){
    echo $file, "\n";
}


Expected result:
----------------
Should print:
  one/b/c
  one/b/d


Actual result:
--------------
Prints:
  one/b/c
  one/b/d
  one/b/c
  one/b/d