Never use NAT with IPv6

/**
 * The only reason for using NAT is a lack of addresses.
 * IPv6 does not suffer from a lack of addresses. If I
 * find that anyone is using NAT with IPv6, I would break
 * their kneecaps and poke their eyes out with sharp
 * sticks. I don't really want to go to jail though, so
 * instead, I'll spare myself the effort of support nat
 * traversal magic when IPv6 is involved in hopes this will
 * cause boneheads who would try to use IPv6 NAT to give up
 * since so many things will stop working. I'm sick of
 * working around all of the problems that NATs introduce.
 */