Generate an xz tar archive of the distribution

* configure.ac (AM_INIT_AUTOMAKE): Replace dist-bzip2 with dist-xz.
* Makefile.am: Update srpm target.
* make-dist: Update for dist-xz.
* strace.spec: Update Source tag.
* debian/watch: Update regexp.
* .gitignore: Add strace-*.tar.xz.
6 files changed