Add FreeBSD periodic(8) configuration

Signed-off-by: Giel van Schijndel <me@mortis.eu>
Add FreeBSD ports build system

Signed-off-by: Giel van Schijndel <me@mortis.eu>
Make sure we're compatible with FreeBSD's 'date' and 'getopt'

Signed-off-by: Giel van Schijndel <me@mortis.eu>