turn default of disable_gnksa_domain_check to on

As new gTLDs are hitting the root zone (~20 this week, and up to 1400
within the next few month at a rate of ~20/week) keeing the list of allowed
TLDs up to date is impossible.

I'll set the default of disable_gnksa_domain_check to TRUE for the next
snapshot/release - that might "break" exisiting filters (as one of the
most used features of the GNKSA filter was the valid tld check).

Latest if RFC 6530ff. someday hits usenet (I fear it will do) the GNKSA
filter needs to be extended/rewritten - or entirely dropped. I'm not going
to take care about the GNKSA code, if nobody maintains it (code hasn't been
touched for ~10 years, still treats some valid addresses as invalid) it
will be removed when internationalized local-parts will be allowed and
nobody took care about the parser.

urs
-- 
"Only whimps use tape backup: _real_ men just upload their important stuff
 on ftp, and let the rest of the world mirror it ;)" - Linus