correct timestamp for packets tapped by bpf

[Joerg Sonnenberger]

On Thu, Jul 27, 2006 at 09:50:06PM +0800, Sepherosa Ziehau wrote:
> http://leaf.dragonflybsd.org/~sephe/bpf.c.diff
> 
> Above patch makes same packet tapped by different bpf devices have
> same timestamp.  Obtained from FreeBSD.
> 
> Please review it.  If no objection comes, it will be committed two days 
> later.

It is fine. Please commit it.

Joerg