Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

- Use size_t instead of int when appropriate;
- Use C99 sparse initialization.

With these changes ifconfig(8) is WARNS=2 clean.

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