Petr, since you're listed as patch author, do you know if this feature worked in the past?
tcpdump worked somehow, but I do not remember exactly, it is 4 years ago, see #448695. Probably, the <net/pfvar.h> used to need <net/if_pflog.h>.It is not needed any longer. It looks like the proper fix is just to discard 50_kfreebsd.diff (after quilt pop -a -f) from series.
Dererk, please could you test such tcpdump with your custom kernel ? Cheers Petr