This interface can be implemented by types which are capable of
attaching compiled BPF filters to themselves, such as
x/net/ipv{4,6}.PacketConn.

Fixes golang/go#19912

Change-Id: I4674c3e312c173d5a7a3beb3cd53704f8c08e29b
Reviewed-on: https://go-review.googlesource.com/44972
Run-TryBot: Matt Layher <mdlayher@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Mikio Hara <mikioh.mikioh@gmail.com>