Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Remove IPX over IP tunneling pieces from ifconfig(8), omitted portion of
previous commit:

Remove IPX over IP tunneling support, which allows IPX routing over IP
tunnels, and was not MPSAFE. The code can be easily restored in the
event that someone with an IPX over IP tunnel configuration can work
with me to test patches.

This removes one of five remaining consumers of NET_NEEDS_GIANT.

Approved by: re (kensmith)

Spotted by: Artem Naluzhny <tutat nhamon dot com dot ua>

point-to-point address should come from ifa_dstaddr

use getifaddrs from libc instead of private code

Reviewed by: bms
MFC after: 1 month

Overhaul to cleanup some of the tangled logic that's grown over the years.

o break per-address family support out into separate files
o modularize per-address family and functional operations using
a registration mechanism; this permits configuration according
to which files you include (but beware that order of the files
is important to insure backwards compatibility)
o many cleanups to eliminate incestuous behaviour, global variables,
and poor coding practices (still much more to fix)

The original motivation of this work was to support dynamic addition
of functionality based on the interface so we can eliminate the various
little control programs and so that vendors can distribute ifconfig
plugins that support their in-kernel code. That work is still to be
completed.

o Update 802.11 support for all the new net80211 functionality; some
of these operations (e.g. list *) may be better suited in a different
program