Third-party notices

pint-cf’s unit-definition data (src/pint_cf/resources/registry/udunits2*.txt) is generated from UDUNITS-2’s own XML unit database (see tools/xml/*.xml and tools/xmlrd.py in this repository) and is redistributed under UDUNITS-2’s own copyright and license terms, reproduced in full in src/pint_cf/resources/registry/UDUNITS2-COPYRIGHT.txt (also included in the installed package).