Description:
------------
The following line always returns FALSE:

$info = curl_getinfo($ch, CURLINFO_HEADER_OUT);

Reproduce code:
---------------
$request = <<<EOD
<?xml version="1.0" encoding="UTF-8"?>
<methodCall>
<methodName>menu.getAnswer</methodName>
<params/>
</methodCall>

EOD;

$header[] = "Content-type: text/xml";
$header[] = "User-Agent: foobar";
$ch = curl_init($url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, $header);
curl_setopt($ch, CURLOPT_HEADER, true);
curl_setopt($ch, CURLOPT_POSTFIELDS, $request);
$response = curl_exec($ch);
$info = curl_getinfo($ch, CURLINFO_HEADER_OUT);

Expected result:
----------------
According to the documentation this option has been available since version 5.1.3, so I expect to see the request headers which were sent out.

Actual result:
--------------
The result is always FALSE.