v2.7 join using

hi, in v2.7 join not working with USING (only with ON):
```php
$this->_query .= " " . $joinType. " JOIN " . $joinStr ." on " . $joinCondition;
```

```php
protected function _buildJoinOld() {
.
.
.
$this->_query .= " " . $joinType . " JOIN " . $joinStr . 
                (false !== stripos($joinCondition, 'using') ? " " : " on ")
                . $joinCondition;
```