whois ftbfs if HAVE_LIBIDN=1 is used

[ken@…]

We list HAVE_LIBIDN=1 as an option, so it doesn't get picked up by automated testing. But I had been using it. 'make' now complains:

Makefile:38: *** Please fix your build system to stop defining HAVE_LIBIDN!.  Stop.

and the full content of that part of the Makefile is:

# libidn support has been autodetected since 5.2.18
ifdef HAVE_LIBIDN
$(error Please fix your build system to stop defining HAVE_LIBIDN!)
endif

So just remove the Command Explanation.

[ken@…]

r21226