Makefile.in: add strdup.o target ; remove getaddrinfo.o nonexistent target
DNS: fix a typo
NDOize BOOTP, DHCPv6, DNS, PIM and sFlow decoders

Also add/remove tabs in a few involved functions to justify indentation.
OpenFlow: add IANA-allocated TCP port

OF specifications 1.0.2 and 1.3.3 use a different port number. That
said, the old port is still likely to be seen in the wild after 4 years
of deployment. Let tcpdump recognize both for a while.