Hey,
since IPv6 is getting more populair wouldn't it be a good idea to have 
an mk.conf option ' INET6' so that if you have this in your mk.conf 
pkgsrc will automatically installed Ipv6 version (a good example of this 
is the postfix INET6 mk.conf options would would then be deprecated by 
this newer one). It would require you to set this value only once and 
not for every package that you want to install a INET6 version of.
What do you guys think?

Regards,
Douwe