Fixed a bug in PHPUnit_Framework_Constraint_Count
For instances of Iterator, it called [iterator_count](php.net/manual/en/function.iterator-count.php),
which (unfortunately) changes the instance's key. This fix `rewind`s the iterator's key to where it was
Merge pull request #1125 from asystance/fix-CountIterator-3.7

Fixed a bug in PHPUnit_Framework_Constraint_Count