addrwatch: new package

addrwatch: new package

Maintainer: Ondrej Caletka / @Oskar456
Compile tested: TurrisOS 3.1 (fork of OpenWRT Chaos Calmer), Trunk (both uClibC and musl)
Run tested: mpc85xx - Turris 1.0 -  TurrisOS - no problems observed
Upstream: https://github.com/fln/addrwatch / @fln

Description:

This is a tool similar to arpwatch. It's main purpose is to monitor network
and log discovered ethernet/ip pairings.

The package has been UCIfied, care has been taken to reload the deamon
every time an interface goes up or down.

Signed-off-by: Ondřej Caletka <ondrej@caletka.cz>