Layout broken on Windows

[selfthinker]

The sidebar appears under the content if this template is installed on a Windows machine.
I get a 404 for the layout.js and a JavaScript error. In bootstrap.php this line

$filepath = DOKU_TPL . 'js' . DIRECTORY_SEPARATOR . $filename;

should not contain a DIRECTORY_SEPARATOR as it's a URL for a web resource and should therefore always be using a / instead.