Resolve "Switch to IDNA2008 non-transitional processing (and use libidn2 for that)"
This MR transition from libidn to libidn2 to upgrade IDNA to IDNA2018 (transitional). It contains new dig option +idnin, which allows to process invalid domain names much like dig without IDN support.
Originally submitted as !56 (closed) by @pemensik.
Closes #26 (closed)