[pcap-ng-format] Appendix C of the pcap-NG spec should just point to www.tcpdump.org/linktypes.html

[Guy Harris]

Now that

	http://www.tcpdump.org/linktypes.html

exists, the pcap-NG spec should point to it, rather than having the list of link-layer header types and values in an appendix.  That page is more likely to be up-to-date (I tend to update it shortly after a new LINKTYPE_ value is assigned).  It doesn't include the "reserved" values, but it does say "All other values are reserved for current or future uses."; if the people who "own" those values submit a specification for them, I'll update the page to describe them.

That page also handles the Appendix D stuff, in that the items on that page specify what the link-layer headers are (some need more work, but most of them should be sufficient).