CURLOPT_VERBOSE(3) on macOS

The text 76daf77bf7cb, 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.

set verbose mode on/off

CURLOPT_VERBOSE(3) on macOS now