Nuke the token bucket filter code. Attempting to request rate limiting
by the token bucket filter will result in EINVAL being returned.

If you want to rate-limit traffic in future, use ALTQ or dummynet; this
isn't a general purpose QoS engine.

Preserve the now unused fields in struct vif so as to avoid having to
recompile netstat(1) and other tools.

Reviewed by: Pavlin Radslavov, Bill Fenner