dispatch_source_create(3) on macOS

The text e0177c641105, as OS X 10.11.6, OS X 10.11.5, OS X 10.11.4, OS X 10.11.3, OS X 10.11.2, OS X 10.11.1, OS X 10.11 shipped it.

dispatch event sources

dispatch_source_create(3) on macOS now