Remove $FreeBSD$: two-line .h pattern

Remove /^\s*\*\n \*\s+\$FreeBSD\$$\n/

libifconfig: Set error in ifconfig_get_groups

This should return -1 with OTHER/ENOMEM set in the handle when malloc
fails, like everywhere else in libifconfig.

Reviewed by: kp
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D28964

Move list_cloners to libifconfig

Move list_cloners() from ifconfig(8) to libifconfig(3) where it can be
reused by other consumers.

Reviewed by: kp
Differential Revision: https://reviews.freebsd.org/D26858

libifconfig: multiple feature additions

Added the ability to:

* Create virtual interfaces
* Create vlan interfaces
* Get interface fib
* Get interface groups
* Get interface status
* Get nd6 info
* Get media status
* Get additional ifaddr info in a convenient struct
* Get vhids
* Get carp info
* Get lagg and laggport status
* Iterate over all interfaces and ifaddrs

And add more examples, too.

Note that this is a backwards-incompatible change. But that's ok, because it's
a private library.

MFC after: 3 weeks
Sponsored by: Spectra Logic Corp
Differential Revision: https://reviews.freebsd.org/D14463

libifconfig: fix ifconfig_set_metric

Due to a copy/paste error, ifconfig_set_metric actually set the mtu, not the
metric.

See Also: https://github.com/Savagedlight/libifconfig/issues/48

MFC after: 3 weeks
Sponsored by: Spectra Logic Corp

libifconfig: allow to get original interface name via ifconfig_get_orig_name()

Uses the same method as in tools/tools/ifinfo/ifinfo.c
(via net.link.generic sysctl).

Tested with modified wlandebug(8).

Differential Revision: https://reviews.freebsd.org/D12554

Renumber copyright clause 4

Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.

Submitted by: Jan Schaumann <jschauma@stevens.edu>
Pull Request: https://github.com/freebsd/freebsd/pull/96

libifconfig: style(9) fixes

Also switch from BSD 3-clause to 2-clause license where possible, and
consolidate duplicate 3-clause license into one.

Submitted by: Marie Helene Kvello-Aune <marieheleneka@gmail.com>
Reviewed by: cem, kp
Differential Revision: https://reviews.freebsd.org/D7764

Renaming libifc to libifconfig in response to feedback on initial commit of
this library. Sticking to 'libifconfig' (and 'ifconfig_' as function prefix)
should reduce chances of namespace collisions, make it more clear what the
library does, and be more in line with existing libraries.

Submitted by: Marie Helene Kvello-Aune <marieheleneka@gmail.com>
Differential Revision: https://reviews.freebsd.org/D7742
Reviewed by: cem, kp