According to the latest KAME release, recently added to NetBSD, it isn't
permitted to directly include netinet6/in6.h anymore. The RFCs and drafts all say to include netinet/in.h and that will define the ipv6 goop if the host supports it. Rather than break (broken) OSs, I added a check for NetBSD in configure that will force the definitions of ISC_PLATFORM_HAVENETINET6IN6H and LWRES_PLATFORM_HAVENETINET6IN6H to be #undef. This isn't really as clean as I'd like. I'd rather be hard and say an OS that requires direct include of netinet6/in6.h is broken, and remove it fully from our code.