add exit parameter on sendHeaders

Hello, i have added one optional 'exit' parameter to sendHeaders method to exit from php after send headers.

public function sendHeaders($exit=null)
{
if($exit===null) $exit=false;
$return=false;
if(headers_sent()) $this->sent=true;

if(!$this->sent)
{
foreach($this->buffer as $part)
if(strlen($part[1]) > 0)
header($part[0] . ': ' . $part[1]);
else
header($part[0]);
$this->sendCookies();
$return=true;
}

if($exit) exit();

return $return;
}