Possible bug with _trans_depth transactions

[eluser]phazei[/eluser]
http://ellislab.com/forums/viewthread/101648/#541064

I looked through the code all over DB_driver.php

_trans_depth has a default value of 0.

It is only incremented if ($this->_trans_depth > 0)

So it never increments, ever. Thus nested transactions get
committed by the first trans_complete() rather than the outer most one.

To fix the 'if' on line 497 should be removed.

CI1.7.0