04def62430
- Bring IPsec support from the ports collection [1]. - Bring -o ("once only") option from the ports collection [2]. - Adopt the Makefile framework into usr.bin/nc/Makefile. - Add a knob to control whether to build nc(1), NO_NETCAT. - Bump __FreeBSD_version so ports collection can detect this change. Original patchset are contributed to the ports collection by: [1] nectar, [2] joerg. Note: WARNS?=6 patchset spined off in this commit, in order not to take too many files off the vendor branch.