Import libarchive-3.1.2 as wip/libarchive.

The libarchive library features:

* Support for a variety of archive and compression formats ?.
* Robust automatic format detection ?, including archive/compression
  combinations such as tar.gz.
* Zero-copy internal architecture ? for high performance.
* Streaming architecture eliminates all limits on size of archive, limits on
  entry sizes depend on particular formats.
* Carefully factored code to minimize bloat when programs are statically linked.
* Growing test suite ? to verify correctness of new ports.
* Works on most POSIX-like systems (including FreeBSD, Linux, Solaris, etc.)
* Supports Windows, including Cygwin, MinGW, and Visual Studio.

The bsdtar and bscpio command-line utilities are feature- and performance-
competitive with other tar and cpio implementations:


* Reads a variety of formats, including tar, pax, cpio, zip, xar, lha, ar, cab,
  mtree, rar, and ISO images.
* Writes tar, pax, cpio, zip, xar, ar, ISO, mtree, and shar archives.
* Automatically handles archives compressed with gzip, bzip2, lzip, xz, lzma,
  or compress.
* Unique format conversion feature.
+libarchive - latest stable
Add buildlink3.mk.
Update to latest release, 1.4.5. Requires wip/libarchive, because the one
in archivers is too old. Updated patch. From ChangeLog:

----------------------------------------------------------------
1.45
----------------------------------------------------------------

Unix Shell:

 Additions:
  - Added the ability to switch FDS disks for multi-disk games
  - xBR filter options
  - Support for more archive formats through libarchive
  - Differentiated Soft/Hard Reset

 Changes:
  - Removed internal zip and 7zip decoders in favour of libarchive
  - Replaced gtk_key_snooper with key_press_event and key_release_event

 Fixes:
  - 7zip CRC check segfault

Windows Shell:

 Additions:
  - xBR filter options

 Changes:
  - Redundant TV Aspect checkbox removed from NTSC filter dialog
  - Modified default sound settings to avoid desync

libretro:

 Additions:
  - blargg's NTSC filter core option
  - L/R now insert coins on Vs. System games

Core:

 Additions:
  - xBR filter added - Hyllian, notBald

 Fixes:
  - Triangle volume bug in Dendy mode - emu-russia
  - NTSC filter background colour fix - blargg

...for more, read changelog.txt in the source repo.