Patch to enable our tcpdump to handle CARP

[George Neville-Neil]

Howdy,

I've been trying to debug CARP problems of late. I noticed that our tcpdump didn't have CARP
support.  I took and fixed some code from OpenBSD so that our tcpdump can work with 
CARP.  Unlike OpenBSD you have to specify -T carp to read carp packets.  In their version
you specify -T VRRP, because they don't like VRRP.  I decided that we should go with
what most of the industry cares about rather than what OpenBSD cares about.

Patch is here: http://people.freebsd.org/~gnn/tcpdump-carp.diff

Technical comments welcome.

Best,
George