Log Message:
Rather than playing "reserved define whack-a-mole" on NetBSD by trying to
define _ISOC99_SOURCE to mitigate the damage of defining _XOPEN_SOURCE,
just don't define _XOPEN_SOURCE - nothing in the source defines it and
it breaks at least gcc 6.4 on NetBSD-8.0

No PKGREVISION bump as should not affect any building systems