Add xz compression support. * NEWS: Mention xz, as well as lzma (xz will displace lzma). * automake.in (handle_dist): Recognize dist-xz. (make_paragraphs): Map XZ to dist-xz. * doc/automake.texi (Dist): Add dist-xz. (Options): Likewise. * lib/Automake/Options.pm (_process_option_list): Accept dist-xz. * lib/am/distdir.am (dist-xz): New rule. (dist dist-all): Add command to create an xz-compressed tarball. (distcheck): Handle xz-compressed tarballs just like the others. * tests/xz.test: New file, based on nogzip.test. * tests/Makefile.am (TESTS): Add xz.test. Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>