Addition of lzma/xz compression to HEAD

Hello!

Just FYI: noticed addition of lzma directory to BSD.include.dist mtree file.
Well, now it seems to work!

/* Test file size 264 MiB */
	[wep4035] ~> ll /usr/local/tinderbox/jails/9-amd64/9-amd64.tar 
	-rw-r--r--  1 root  wheel  277209600 Apr 20 20:58 /usr/local/tinderbox/jails/9-amd64/9-amd64.tar

/* Cache file in memory */
	[wep4035] ~> cat /usr/local/tinderbox/jails/9-amd64/9-amd64.tar > /dev/null

/* 30 seconds to gzip it */
	[wep4035] ~> time tar -cvzf 9-amd64.tar.tar.gz /usr/local/tinderbox/jails/9-amd64/9-amd64.tar 
	tar: Removing leading '/' from member names
	a usr/local/tinderbox/jails/9-amd64/9-amd64.tar
	30.043u 0.541s 0:15.32 199.6%   37+2093k 0+747io 0pf+0w

/* 64 seconds to bzip2 it */
	[wep4035] ~> time tar -cvjf 9-amd64.tar.tar.bz2 /usr/local/tinderbox/jails/9-amd64/9-amd64.tar
	tar: Removing leading '/' from member names
	a usr/local/tinderbox/jails/9-amd64/9-amd64.tar
	63.454u 0.686s 0:32.09 199.8%   37+2108k 0+650io 1pf+0w

/* And 140 seconds to xz it */
	[wep4035] ~> time tar -cvJf 9-amd64.tar.tar.xz /usr/local/tinderbox/jails/9-amd64/9-amd64.tar
	tar: Removing leading '/' from member names
	a usr/local/tinderbox/jails/9-amd64/9-amd64.tar
	277.625u 0.857s 2:19.26 199.9%  37+2092k 0+432io 0pf+0w

/* Resulting sizes :)))) */
	[wep4035] ~> ll 9-amd64.tar.tar.*
	-rw-r--r--  1 lexx  lexx  84830128 May 11 21:07 9-amd64.tar.tar.bz2
	-rw-r--r--  1 lexx  lexx  97667581 May 11 21:07 9-amd64.tar.tar.gz
	-rw-r--r--  1 lexx  lexx  56366908 May 11 21:10 9-amd64.tar.tar.xz

/* 3.5 seconds to gunzip the file (mostly IO-limited) */
	[wep4035] ~> cat 9-amd64.tar.tar.gz > /dev/null 
	[wep4035] ~> time tar -xvf 9-amd64.tar.tar.gz 
	x usr/local/tinderbox/jails/9-amd64/9-amd64.tar
	2.721u 0.747s 0:03.54 97.7%     42+2365k 3+2116io 0pf+0w
	[wep4035] ~> rm -R usr/

/* 18 seconds to bunzip2 it */
	[wep4035] ~> cat 9-amd64.tar.tar.bz2 > /dev/null
	[wep4035] ~> time tar -xvf 9-amd64.tar.tar.bz2 
	x usr/local/tinderbox/jails/9-amd64/9-amd64.tar
	18.136u 0.999s 0:09.59 199.3%   37+2110k 1+2116io 0pf+0w
	[wep4035] ~> rm -R usr/

/* And only 10 seconds to xzdec it */
	[wep4035] ~> cat 9-amd64.tar.tar.xz > /dev/null
	[wep4035] ~> time tar -xvf 9-amd64.tar.tar.xz
	x usr/local/tinderbox/jails/9-amd64/9-amd64.tar
	10.304u 0.771s 0:05.59 198.0%   38+2164k 3+2116io 0pf+0w
	[wep4035] ~> rm -R usr/


Thanks to all involved in bringing it to HEAD!

Alexey.

P.S. I'm not claiming any statistical validity of provided timings nor
that the testing procedure is correct. It is just to show that tar in HEAD
now works with lzma/xz compression.