CURLOPT_CONV_TO_NETWORK_FUNCTION(3) on macOS

The text d838dc567886, 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.

convert data to network from host encoding

CURLOPT_CONV_TO_NETWORK_FUNCTION(3) on macOS now