* freebsd4/sys/{if_sppp.h,if_spppsubr.c}: supported PPPv6 for   kernel level PPP.
* freebsd4/sys/{if_sppp.h,if_spppsubr.c}: supported PPPv6 for
  kernel level PPP.

MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame,MarginC/kame