#1108 fix for pdosqlexec doesn't throw exception

Fix for pdosqlexec doesn't throw exception for the non-first SQL instruction.

http://www.phing.info/trac/ticket/1108

When pdosqlexec task process a dbdeploy file and we have a wrong SQL instruction but not the first instruction, PDO doesn't throw exception as explained in this bug ​https://bugs.php.net/bug.php?id=61613

To skip this bug, we can split the SQL file for a instruction for each delimiter.

Adding this control in DummyPDOQuerySplitter it works like a charm, the MySQL errors are showed.