CURLOPT_HEADEROPT(3) on macOS

The text 9321151254f0, as OS X 10.11.6, OS X 10.11.5, OS X 10.11.4, OS X 10.11.3, OS X 10.11.2, OS X 10.11.1, OS X 10.11, OS X 10.10.5 shipped it.

set how to send HTTP headers

CURLOPT_HEADEROPT(3) on macOS now