MFC: merge in all new features and improvements into mkuzip(8) from current,
which includes:

o LZMA compression;
o block de-duplication;
o performance improvements;
o multi-thread support.

This includes the following revisions:
r295943,r296626,r296628,r296810,r298504,r298505,r298577

Suggested by: emaste

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

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

Build usr.bin/ with WARNS=6 by default.

Also add some missing $FreeBSD$ to keep svn happy.

Make WARNS=6 clean, which should make it compiling on amd64.

Submitted by: Matteo Riondato <rionda@gufi.org>

Fix build: s/mkunzip.8/mkuzip.8/

Normalize the makefile.

Reviewed by: sobomax

Add mkuzip(8), non-GPL utility to compress filesystem images for use with
geom_uzip module. This is based on utility I wrote some 3 years ago for a
hack for md(4), which functionally was close to what geom_uzip does today.

Since I don't have a time to test that it compiles/works on other arches,
stick it to i386 only. Will do it later.

Unlike original cloop util, this one embedds FreeBSD-compatible shell code
into the generated image, not Linux one. Unfortunately severe space
restriction imposed by the CLOOP format doesn't allow to put conditional
code which will work both on Linux and FreeBSD. In fact it was quite a
challenge to fit necessary FreeBSD code into 127 bytes. ;-)