faith(4) / faithd(8) removal

[Alexander V. Chernikov]

Hello everyone.

I'd like to remove faith (IPv6/v4 translator) from base.

* It does not seem like a proper way to translate between IPv4/IPv6 traffic.
   There are several well-documented (and already implemented) technologies:
     Stateful/stateless NAT64 (rfc 6146,  6145), 464XLAT (6877).
     Unfortunately, we don't have in-kernel NAT64 implementation, but 
there are
    some userland-base one, like net/tayga64.
* It does complicate IPv6 processing path
* It does not seem to be used: last non-trivial commit was 10 years ago 
(126781).
* OpenBSD removed it in 2013: 
http://cvsweb.openbsd.org/cgi-bin/cvsweb/src/sys/net/Attic/if_faith.c

If there are no objections I'll remove it in a week.