CURLOPT_READFUNCTION(3) on macOS

The text cd6ecaab8ff7, 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.

read callback for data uploads

CURLOPT_READFUNCTION(3) on macOS now