Merge projects/ipfw to HEAD.

Merge projects/ipfw to HEAD.

Main user-visible changes are related to tables:

* Tables are now identified by names, not numbers.
 There can be up to 65k tables with up to 63-byte long names.
* Tables are now set-aware (default off), so you can switch/move
 them atomically with rules.
* More functionality is supported (swap, lock, limits, user-level lookup,
 batched add/del) by generic table code.
* New table types are added (flow) so you can match multiple packet fields at once.
* Ability to add different type of lookup algorithms for particular
 table type has been added.
* New table algorithms are added (cidr:hash, iface:array, number:array and
 flow:hash) to make certain types of lookup more effective.
* Table value are now capable of holding multiple data fields for
  different tablearg users

Performance changes:
* Main ipfw lock was converted to rmlock
* Rule counters were separated from rule itself and made per-cpu.
* Radix table entries fits into 128 bytes
* struct ip_fw is now more compact so more rules will fit into 64 bytes
* interface tables uses array of existing ifindexes for faster match

ABI changes:
All functionality supported by old ipfw(8) remains functional.
 Old & new binaries can work together with the following restrictions:
* Tables named other than ^\d+$ are shown as table(65535) in
 ruleset in old binaries

Internal changes:.
Changing table ids to numbers resulted in format modification for
 most sockopt codes. Old sopt format was compact, but very hard to
 extend (no versioning, inability to add more opcodes), so
* All relevant opcodes were converted to TLV-based versioned IP_FW3-based codes.
* The remaining opcodes were also converted to be able to eliminate
 all older opcodes at once
* All IP_FW3 handlers uses special API instead of calling sooptcopy*
 directly to ease adding another communication methods
* struct ip_fw is now different for kernel and userland
* tablearg value has been changed to 0 to ease future extensions
* table "values" are now indexes in special value array which
 holds extended data for given index
* Batched add/delete has been added to tables code
* Most changes has been done to permit batched rule addition.
* interface tracking API has been added (started on demand)
 to permit effective interface tables operations
* O(1) skipto cache, currently turned off by default at
 compile-time (eats 512K).

* Several steps has been made towards making libipfw:
  * most of new functions were separated into "parse/prepare/show
    and actuall-do-stuff" pieces (already merged).
  * there are separate functions for parsing text string into "struct ip_fw"
    and printing "struct ip_fw" to supplied buffer (already merged).
* Probably some more less significant/forgotten features

MFC after:	1 month
Sponsored by:	Yandex LLC