Update!!! if_bridge(4) modefied.

Bridge is capable to inspect rfc-2516 (PPPOE) frames, if they
contain IPv[46] PDU. If datagram is dectected, then ipfw(4)
proccesses it.

enables layer2 filtering. Further, if dummynet(4) is enabled,
then from rfc-1661 downstream originating datagrams are diverted
end encapsulated by Ethernet PCI, but typefield is then changed
from ETHERTYPE_PPPOE to ETHERTYPE_IP[V6].