Since 1.5, we display the html lang code in our default core templates as lower case.
Example <html lang=en-gb
the code used is <html lang="<?php echo $this->language; ?>"
This comes from document.php where the method is using strtolower
public function setLanguage($lang = 'en-gb')
{
$this->language = strtolower($lang);
return $this;
}
I see no reason for forcing lowercase for the country code.
See
http://www.ietf.org/rfc/bcp/bcp47.txt
https://www.w3.org/International/articles/language-tags/index.en
Patch is easy.
What do you think?
JM