add CR payload decoder. fix ID payload decode.
have __attribute__((__packed__)) for align picky arch
(tcpdump.org code has better fix with lots of memcpy, however,
tcpdump.org version needs more verfication).
basically, sync with kame tree.
- isakmp: print CERT and SIG payload. fix IPsec-AH algorithm type.
- rt6: avoid duplicated IPv6 src/dst.
sync with tcpdump.org.
XXX we need to think about future synchronization with tcpdump.org...
- more length overflow check for ip6 related parsing
- protocol decode fixes
- add dhcp6 parser
XXX how should we maintain usr.sbin/tcpdump for years to come?
relationship with www.tcpdump.org codebase?