Bug 726458 - Fix build problem on FreeBSD

Define _BSD_SOURCE does not make fchmod() available on FreeBSD. Change
_POSIX_C_SOURCE to 200809L so we can build it on FreeBSD.

Signed-off-by: Hans Breuer <hans@breuer.org>
(cherry picked from commit 4e948cc8)

Conflicts:
	app/load_save.c