CURLOPT_AUTOREFERER(3) on macOS

The text 9499a4ccd71d, as macOS 10.12.5, macOS 10.12.4, macOS 10.12.3, macOS 10.12.2, macOS 10.12.1, macOS 10.12 shipped it.

automatically update the referer header

CURLOPT_AUTOREFERER(3) on macOS now