catopen(3) on macOS

The text d21425776b26, as Mac OS X 10.1.5, Mac OS X 10.1.4, Mac OS X 10.1.3, Mac OS X 10.1.2, Mac OS X 10.1.1, Mac OS X 10.1, Mac OS X 10.0.4, Mac OS X 10.0 shipped it.

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catopen(3) on macOS now