Sets the preferred name for the HTTP header.
Header names are case-insensitive, but for maximum compatibility they should follow "common form" (see RFC 2616, section 4.2).
Header handling is being shifted to a Symfony response object.
function _drupal_set_preferred_header_name($name = NULL) {
static $header_names = array();
if (!isset($name)) {
return $header_names;
}
$header_names[strtolower($name)] = $name;
}