maint: distribute .xz tarballs, not .bz2 ones Many GNU packages are moving towards xz-compressed tarballs, so let's follow suit, by dropping the creation and distribution of a bzip2-compressed tarball and switching to xz instead. For compatibility and safeness, we will continue to create and distribute a gzip-compressed tarball as well. * configure.ac (AM_INIT_AUTOMAKE): Drop `dist-bzip2', add `dist-xz'. * NEWS: Update. Suggested by Jim Meyering.