More lenient IDNA processing in dig

It's annoying when dig gives up with an error if there is a problem with IDNA conversion. Rather than having to re-run it with +noidnout etc. it would be nice if dig would automatically fall back to printing the unconverted name. (And similarly for IDNA input names.)

Users who need to script IDNA error / syntax checks can use the idn2 tool, which provides much more specific options than dig can. (This is a minor incompatibility with the old behaviour.)