cleanup POSIX/XOPEN defines for switch to C99

Authored by kgardas on Mar 29 2016, 5:21 AM.

Description

cleanup POSIX/XOPEN defines for switch to C99

Summary:
This patch cleans up various POSIX and XOPEN defines.
We aim to switch to C99 solely and for this the lowest version
of supported POSIX/XOPEN is:
_XOPEN_SOURCE 600
_POSIX_C_SOURCE 200112L

Test Plan:
tested on Solaris 11 and OpenBSD 5.9. Should be good
also on Solaris 10, FreeBSD and DragonFlyBSD. We need to test
on Mac OS X, Linux and MinGW

Reviewers: austin, bgamari, erikd, hvr

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2056