Check if the prolog attributes are passed to the prolog object in OPT.

>>>>templates/test.tpl
<?xml version="1.0" standalone="no" encoding="UTF-8" ?>
<foo>
</foo>

>>>>data.php
$this->tpl->prologRequired = false;

>>>>expected.txt
OUTPUT

>>>>result.txt
<?xml version="1.0" standalone="no" encoding="UTF-8" ?>
<foo>
</foo>