Implement anti-replay algorithm with ESN support

As RFC 4304 describes there is anti-replay algorithm responsibility
to provide appropriate value of Extended Sequence Number.

This patch introduces anti-replay algorithm with ESN support based on
RFC 4304, however to avoid performance regressions window implementation
was based on RFC 6479, which was already implemented in FreeBSD.

To keep things clean and improve code readability, implementation of window
is kept in seperate functions.

Submitted by: Grzegorz Jaszczyk <jaz@semihalf.com>

Patryk Duda <pdk@semihalf.com>

Reviewed by: jhb
Differential revision: https://reviews.freebsd.org/D22367
Obtained from: Semihalf
Sponsored by: Stormshield