CURLOPT_CHUNK_BGN_FUNCTION(3) on macOS

The text 6d441754cfd8, 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.

callback before a transfer with FTP wildcardmatch