em0, VLAN and bpf(?) trouble w/RELENG_5

[astesin at ukrtelecom.net]

> So now I have RELENG_5 as of today
> 
> 1. No problems with large frames. Bing -s 2000 -S 4000 -e 
> 5000 works fine through vlan0.
> 
> 2.  trafshow -i vlan0
>      ... silence ...
> 
>     Vlan0 hangs.

3. trafshow -p -I vlan0 works fine