get_headers issue with large files

Adding Remote files will use a lot of memory beacuase the get_headers Function uses a GET request instead a http HEAD Request to retrieve the content-length Header of the Remote File.

So we should change the code of the remote_filesize function like this (if not we get a Internal Server Error):

### Function: Get Remote File Size
if(!function_exists('remote_filesize')) {
        function remote_filesize($uri) {
                $contentLength = __('unknown', 'wp-downloadmanager');
                $ch = curl_init($uri);
                curl_setopt($ch, CURLOPT_NOBODY, true);
                curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
                curl_setopt($ch, CURLOPT_HEADER, true);
                curl_setopt($ch, CURLOPT_FOLLOWLOCATION, true);
                $data = curl_exec($ch);
                curl_close($ch);
                if ($data === false) {
                        return $contentLength;
                }
                if (preg_match('/Content-Length: (\d+)/', $data, $matches)) {
                        $contentLength = (int)$matches[1];
                }
                return $contentLength;
        }
}

Can you fix this in the next releases?

https://wordpress.org/plugins/wp-downloadmanager/