CURLOPT_HEADER(3) on macOS

The text 11a5c8b8ec3b, 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.

pass headers to the data stream

CURLOPT_HEADER(3) on macOS now