CURLOPT_CUSTOMREQUEST(3) on macOS

The text 15b58dc3f2a4, 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.

custom string for request

CURLOPT_CUSTOMREQUEST(3) on macOS now