dig output should not display IDNs unless explicitly requested

The 9.13 behaviour when linked with libidn appears to be a change from earlier versions, where dig will now automagically convert punycode labels into unicode, but worse, fail to do so and terminate with an error if the conversion cannot be done in the current locale.

(as noted by Vixie on the DNS Operations list on 2018/10/31).

I think the default should be to not do this unless the +idnout option is passed.