Log Message:
libidn2: Update to 2.3.0

* Version 2.3.0 (released 2019-11-14)

** Mitre has assigned CVE-2019-12290 which was fixed by
   the roundtrip feature introduced in 2.2.0 (commit 241e8f48)

** Update the data tables from Unicode 6.3.0 to Unicode 11.0

** Turn _idn2_punycode_encode, _idn2_punycode_decode
   into compat symbols (Fixes #74)