Support $title_heading levels in panels-pane.tpl.php

adaptivetheme/at_core/templates/panels-pane.tpl.php has a bug regarding the pane title.

As of panels 7.x-3.4, users can change the pane title's tag to something different than <h2>.

Currently, adaptivetheme/at_core/templates/panels-pane.tpl.php code reads as:

<?php print render($title_prefix); ?>
  <?php if ($title): ?>
    <h2<?php print $title_attributes; ?>><?php print $title; ?></h2>
  <?php endif; ?>
<?php print render($title_suffix); ?>

It needs to be changed to:

<?php print render($title_prefix); ?>
  <?php if ($title): ?>
    <<?php print $title_heading; ?><?php print $title_attributes; ?>>
    <?php print $title; ?>
    </<?php print $title_heading; ?>>
  <?php endif; ?>
<?php print render($title_suffix); ?>

I'm working behind a proxy so I'm not really able to create a proper patch using git, but hopefully the attached file will suffice.