IDN support in host cannot be disabled

Summary

IDN support in host cannot be disabled by parameter or environment.

Steps to reproduce

• build bind --with-libidn2
• man host, search for IDN.
• IDN_DISABLE=1 host háčkyčárky.cz

What is the current bug behavior?

IDN is not disabled, name is decoded and result is decoded as well.

What is the expected correct behavior?

IDN library is not used and name is passed to resolver as it was passed to command line.

Possible fixes

Proposed in merge request !800 (merged)