Fixed the internal server error 500 that occurs if fastcgi is used on a webserver.

Therefore, I have replaced two lines of the new file product_thumb.php:
header("Status: 304 Not Modified");
header($httpProtocol . " 304 Not Modified");

With the following code:
if (substr(php_sapi_name(), 0, 3) == 'cgi') {
header("Status: 304 Not Modified");
} else {
header($httpProtocol . " 304 Not Modified");
}

Fore more details about this bug see http://bugs.php.net/bug.php?id=36705

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