Remove $FreeBSD$: one-line sh pattern

Remove /^\s*#[#!]?\s*\$FreeBSD\$.*$\n/

Change the default locale to C.UTF-8

The C.UTF-8 locales is the same as the actual C locale except it does support
the unicode character set. But the collation etc are still the same as the C
locale one.

Reviewed by: many
Approved by: many
Differential Revision: https://reviews.freebsd.org/D26973

login.conf(5): update commented-out standard, too

MAIL now has a mail capability, instead, as of r357560.

login.conf(5): set a default PATH for the daemon class

This is a sensible default used by, e.g., cron(8), and useful if one wanted
to honor it.

This is a part of D21481.

Submitted by: Andrew Gierth <andrew_tao173.riddles.org.uk>

login.conf(5): split MAIL env var out into a "mail" capability

This allows it to be easily suppressed in, e.g., the "daemon" class where it
will not be properly expanded.

This is a part of D21481.

Submitted by: Andrew Gierth <andrew_tao173.riddles.org.uk>

motd: Generate from template to /var/run

Update login(1), its manual pages, similar utilities, and motd.5 to refer to
the new location.

Suggested by: delphij@ (re: r349256)
Reviewed by: bcr (manpages), delphij
Differential Revision: https://reviews.freebsd.org/D20721

Move fbtab, login.conf, and motd to usr.bin/login/

Approved by: Approved by: re (gjb), bapt (mentor), will (mentor)
Differential Revision: https://reviews.freebsd.org/D16947