Description:
------------
IteratorIterator has a method `seek` that matches the signature for implementing 
SeekableIterator, but it doesn't implement the interface.

Also, subclasses of IteratorIterator do not inherit the seek method. This breaks 
the rules for inheritance.

I'm not sure how to propose fixing it at this point.  This should have been caught 
before being released. Like much of the SPL, this was not properly thought out and 
tested.

Test script:
---------------
$iterator = new IteratorIterator(
    new EmptyIterator()
);

var_dump($iterator instanceof SeekableIterator);
var_dump(method_exists($iterator, 'seek');

$iterator = new NoRewindIterator(
    new EmptyIterator()
);
var_dump(method_exists($iterator, 'seek');


Expected result:
----------------
bool(true);
bool(true);
bool(true);

Actual result:
--------------
bool(false);
bool(true);
bool(false);