CURLOPT_SOCKS5_GSSAPI_NEC(3) on macOS

The text ad0098ed845f, 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.

set socks proxy gssapi negotiation protection