IPv6 changes into kernel

[itojun_(_at_)_iijlab_(_dot_)_net]

	Hello, this is itojun.  I'll be bringing KAME IPv6 stack into
	openbsd-current kernel code (userland commits should follow soon).
	I confirmed:
	- GENERIC kernel (which has IPv4 only) works fine
	- GENERIC.v6 kernel compiles and works fine, if you have KAME userland
	  fixes separately
		twists will be listed into sys/netinet6/{IMPLEMENTATION,TODO}
	- userland build may experience some breakage due to changes in header
	  files, to be resolved

	GENERIC.v6 should be integrated into GENERIC, after all the userland
	IPv6-support fixes are in place and kernel gets stabilized.

	Please refrain from making too much changes to sys/netinet*
	tree (even if cosmetic), as we (KAME team) share these
	code among *BSD.  If you keep the tree untouched,
	that will help us upgrade to more recent KAME tree easier.

	I'll place a cvs tag (not a branch tag) called "kame_19991208"
	into the tree for future references.

itojun