Description:
------------
PDO_ODBC, connecting to a DB2 database, does not support PDO::beginTransaction() / PDO::rollBack().

I tested the same code against both PDO_ODBC and PDO_SQLITE, but only PDO_SQLITE handled the rollback correctly

The required functionality for transaction management in PDO_ODBC should be available in the ODBC 3.0 SQLEndTran() function - see http://publib.boulder.ibm.com/infocenter/db2help/topic/com.ibm.db2.udb.doc/ad/r0000586.htm for more details.

Unit test pdo_017 has been added to the ext/pdo/tests and ext/pdo_odbc/tests branches to track this functionality.

Reproduce code:
---------------
<?php
$conn = new PDO('odbc:SAMPLE', 'db2inst1', 'ibmdb2');
//$conn = new PDO('sqlite:/home/daniels/bust');
$conn->exec('CREATE TABLE test (id INT)');
$conn->exec('INSERT INTO test(id) VALUES (1)');
$conn->exec('INSERT INTO test(id) VALUES (2)');
$conn->exec('INSERT INTO test(id) VALUES (3)');
$conn->beginTransaction();
function countRows($conn, $action) {
    $sql = "SELECT COUNT(*) FROM test";
    $stmt = $conn->query($sql);
    $num = $stmt->fetchSingle();
    return "Counted $num rows after $action.\n";
}
echo countRows($conn, 'insert');
$conn->exec('DELETE FROM test');
echo countRows($conn, 'delete');
$conn->rollBack();
echo countRows($conn, 'rollback');
?>


Expected result:
----------------
Counted 3 rows after insert.
Counted 0 rows after delete.
Counted 3 rows after rollback.

Actual result:
--------------
Counted 3 rows after insert.
Counted 0 rows after delete.
Counted 0 rows after rollback.