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

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

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

Default to AF_LOCAL instead of AF_INET sockets for non-family-specific
operations. This allows the query operations to work in non-IPv4 jails,
and will be necessary in a future of possible non-INET networking.

Approved by: bz (mentor)

Replace clone_setcallback() with a new function clone_setdefcallback()
that selects a callback from an interface prefix name. This allows us to
report a meaningful error when the user types 'ifconfig wlan0 create',
for example, and also kills some redundant code.

Reviewed by: sam (earlier version)

Fix handling of create operation together with setting other parameters:
o mark cmds/parameters to indicate they are potential arguments to a clone
operation (e.g. vlantag)
o when handling a create/clone operation do the callback on seeing the first
non-clone cmd line argument so the new device is created and can be used;
and re-setup operating state to reflect the newly created device

Reviewed by: Eugene Grosbein
MFC after: 2 weeks

Restore the "plumb" compatibility command, which was lost
due to the recent change by sam@ to clone operations in ifconfig(8).

o replace special handling of clone operations by a clone callback
mechanism
o change vlan cloning to use callback and pass all vlan parameters
on create using the new SIOCREATE2 ioctl
o update vlan set logic to match existing practice

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