Commit 9a269bb3cd1d322a070ef0d6009c980e038e6332
2018-09-18T12:19:02
doc: OS X 10.11 lacked ns time functions According to <https://github.com/zeromq/libzmq/issues/2175>, nanosecond-resolution timestamp functions were introduced in macOS 10.12, so document the last version (OS X 10.11) where they were absent.