unxf 2.2.0 - dependency bump
rpatricia 1.0 is out, and we can use it without any difficulty.
While we're at it, the licenses attribute for RubyGems is
widely-supported by now, so there's no reason to leave it commented
out.
The license is now "GPLv2 or later" (from GPLv2|GPLv3 only), so
it can be used without my approval when/if the GPLv4 is released.
This removes the checks-and-balances I have on the FSF, but is
probably for the better in case GPLv4 protects users' access to
code better than GPLv3 currently does.