CURLINFO_PRIVATE(3) on macOS

The text 33985ffb2775, 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.

get the private pointer

CURLINFO_PRIVATE(3) on macOS now