Bugfix for IN operator in JOIN conditions

$c->addMultipleJoin doesn't support Criteria::IN in conditions e.g. without this patch the code below will throw error `Criteria.php(925): strrpos() expects parameter 1 to be string, array given`.

```php
$c = new Criteria();
$c->addMultipleJoin(array(
        array(AuthorPeer::ID, BookPeer::AUTHOR_ID),
        array(BookPeer::ISBN, array(12, 34), Criteria::IN)
    ), Criteria::LEFT_JOIN);
```

This patch fixes this behavior in Criteria.

In ModelCriteria you can achieve this behavior with some plane sql - I've added test to ensure this is true.
https://github.com/arvenil/Propel/pull/new/in-operator-in-join-conditions#L2R916