Update to 1.22 which adds --xz/-J support for xz compression.
However, xz itself does not have a stable release yet, so don't force
a runtime dependency.
* Update to 1.21. Notable changes:
- Some new flags, e.g. -J for lzma compression and --lzop.
- transformation scope flags
Testsuite fixes from upstream CVS.
* Drop workarounds for no longer supported FreeBSD releases.