[tlbuild] building / including xz into the build process

[Karl Berry]

    > 	http://tukaani.org/xz/

    Seems to be down, 

Yeah.  It was ok yesterday though, so I assume it's purely temporary.
I'll write Lasse if it persists.

    the source that I found on tug are AAFAIS the latest ones:
            www.tug.org/~preining/xz-4.999.8beta.tar.gz 

Yes, that is the latest (and only, at this point).  It (along with
unmodified current releases of lots of other packages) is also at
ftp://tug.org/dist -- completely unofficial but useful :).

Thanks,
karl