CURLOPT_SSLENGINE_DEFAULT(3) on macOS

The text 647ce807e260, 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.

make SSL engine default

CURLOPT_SSLENGINE_DEFAULT(3) on macOS now