Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Add new device method miibus_linkchg, along with a service routine.

* Factor out the object system from new-bus so that it can be used by
non-device code.
* Re-implement the method dispatch to improve efficiency. The new system
takes about 40ns for a method dispatch on a 300Mhz PII which is only
10ns slower than a direct function call on the same hardware.

This changes the new-bus ABI slightly so make sure you re-compile any
driver modules which you use.

$Id$ -> $FreeBSD$

Crap, I knew I was going to forget something: add missing miibus method
description file which slipped through the cracks.

Pointed out by: Doug <Doug@gorean.org>