CFR: fastforwarding locking

[Sam Leffler]

http://www.freebsd.org/~sam/fastforward.patch

These lock the fast forwarding hash table with a lock per hash bucket. 
There is one known issue with these changes: a LOR with the bridge code 
caused by holding a lock across the call to forward the packet.  Also, some 
statistics are not consistently updated.

Beware of overlap with routing table locking changes.

	Sam