curl_multi_init(3) on macOS

The text 2db0988720d3, as Mac OS X 10.7.5, Mac OS X 10.7.4, Mac OS X 10.7.3, Mac OS X 10.7.2, Mac OS X 10.7.1, Mac OS X 10.7 shipped it.

create a multi handle

curl_multi_init(3) on macOS now