CURLMOPT_PIPELINING_SITE_BL(3) on macOS

The text 537d4285ebdf, 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.

pipelining host blacklist

CURLMOPT_PIPELINING_SITE_BL(3) on macOS now