Add better support for retrieving management information from network
interfaces. This creates two new tables in the net.link.generic branch
of the MIB; one contains (essentially) `ifdata' structures, and the other
contains a blob provided by the interface (and presumably used to
implement link-layer-specific MIB variables). A number of things
have been moved around in the ifnet' and ifdata' structures, so
NEW VERSIONS OF ifconfig(8) AND routed(8) ARE REQUIRED. (A simple
recompile is all that's necessary.)

I have a sample program which uses this interface for those interested
in making use of it.