TODO for etdc

Add a signal catcher for QUIT/HUP/INT; before exiting, try to dump the last
packet we collected, if appropriate.  This isn't as easy as it sounds, because
of a race condition.

Add Appletalk address exclude filters.

Allow specification of multiple AppleTalk address filters.

Allow specification of arbitrarily complex combinations of include and
exclude filters with logical operators.  This should probably include
removing the filtering options, and replacing them with a filter
expression.  For example, "etdc (rtmp and src 100.5) or (nbp and not dest 101.5))".

Add decoders for ASP, AFP, AURP, ADSP, ABP, MacIP payload.