mono/mono — pull request #1052 by sethjackson (2014-05-23 04:59:23+00:00)
Title: Don't define _XOPEN_SOURCE on OpenBSD.

mincore() is defined in as a __BSD_VISIBLE API and if _XOPEN_SOURCE is defined this turns off __BSD_VISIBLE APIs.

Not defining _XOPEN_SOURCE turns on __BSD_VISIBLE by default so __BSD_VISIBLE doesn't need to be defined.