dig: setup IDN whenever printing a message

dig: setup IDN whenever printing a message

because dig now uses the netmgr, printing of response messages
happens in a different thread than setup. the IDN output filtering
procedure, which set using dns_name_settotextfilter(), is stored as
thread-local data, and so if it's set during setup, it won't be
accessible when printing. we now set it immediately before printing,
in the same thread, and clear it immedately afterward.