Description:
------------
When using PDO::ATTR_STATEMENT_CLASS the statement object is an object of the user defined class but it's not possible to access it's (non-pdo) methods

Reproduce code:
---------------
<?php
$pdo = new PDO("pgsql:user=zrm dbname=zrm host=localhost");

class myStatement extends PDOStatement
{
	function foo()
	{
		echo __METHOD__;
	}
}

$opts = array();
$opts[PDO::ATTR_STATEMENT_CLASS] = array('myStatement');
$r = $pdo->prepare('SELECT login_id FROM logins', $opts);
var_dump($r->foo());
?>

Expected result:
----------------
myStatement::foo()

Actual result:
--------------
Fatal error: Call to undefined method myStatement::foo()