Description:
------------
See the code attached :
class FubarOK has no problem implementing Iterator. interface NewIterator just extends Iterator and adds nothing, and here comes the fun - an error message when FubarProblem tries to implement NewIterator.

Reproduce code:
---------------
<?php
class FubarOk implements Iterator {
        public function next(){}
        public function key(){}
        public function current(){}
        public function hasMore(){}
        public function rewind(){}
}

interface NewIterator extends Iterator {

}

class FubarProblem implements NewIterator {
        public function next(){}
        public function key(){}
        public function current(){}
        public function hasMore(){}
        public function rewind(){}
}
?>

Actual result:
--------------
PHP Fatal error:  Class FubarProblem must implement interface Traversable as
part of either Iterator or IteratorAggregate in Unknown on line 0