opt:literal and XML comments - it should not generate a nested code.

>>>>templates/test.tpl
<?xml version="1.0" encoding="UTF-8" standalone="yes" ?>
<opt:root>
<opt:literal type="comment">
A text with
<!-- comments -->
</opt:literal>
</opt:root>

>>>>data.php
$this->tpl->printComments = true;

>>>>expected.txt
OUTPUT

>>>>result.txt
<!--
A text with
 comments 
-->