Add shortcode support to Popup (and similar) plugins

The Popup plugin (and I suppose others) lack the support for multilanguage sites.

On thing that would help working out this lack, would be adding support for shortcodes (and let the theme developer sorting out how to get translated content).

This would also help getting dynamic content.

For instance, the Popup plugin could get a specific post-type (by ID) for the contents. title, meta, etc, simply entering a shortcode in the Popover content field.

I've already changed the plugin's code in order to do that, as it's quite an easy customization to do in the page_footer() function, right after the first if-else statement.

Replacing "$content = stripslashes($getoption('popover_content', ''));" with

$tempcontent = $getoption('popover_content', '');
$tempcontent = stripslashes($tempcontent);
$tempcontent = do_shortcode($tempcontent);
$content = $tempcontent;

Does the trick (I'm not sure if the stripslashes() function must be called before or after the do_shortcode() function, as I'm not quite sure what is its purpose, but it works so far).