Description:
------------
According to the docs, readdir(), rewinddir() and closedir() should take at least one argument: the directory handle.

However, these methods are also aliases for the Directory class methods Directory::read(), Directory::rewind() and Directory::close(). Instances of the Directory class hold the directory handle in $this->handle.

Therefore, if no argument is passed, the implementation of these methods  is such that $this->handle is used as the directory handle. However, no check is made to ensure $this is an instance of Directory.

Consequently, calling readdir() etc.. with no arguments from a context where $this->handle just happens to exists will result in unexpected behaviour instead of an error message.

Reproduce code:
---------------
<?php
Class C {
	public $handle;
	function test() {
		// Expecting failure.
		var_dump(readdir());
		var_dump(rewinddir());
		var_dump(closedir());
	}
}

$c = new C;
$c->handle = opendir(getcwd());
$c->test();
?>

Expected result:
----------------
Warning: readdir(): no Directory resource supplied in %s on line 6
bool(false)

Warning: rewinddir(): no Directory resource supplied in %s on line 7
bool(false)

Warning: closedir(): no Directory resource supplied in %s on line 8
bool(false)


Actual result:
--------------
string(1) "."
NULL
NULL