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)

mdoc: reorder sections consistently

Remove unneeded tab after .Ed to make manlint happy.

Reported by: manlint

Add a new bus method, BUS_ADJUST_RESOURCE() that is intended to be a
wrapper around rman_adjust_resource(). Include a generic implementation,
bus_generic_adjust_resource() which passes the request up to the parent
bus. There is currently no default implementation. A
bus_adjust_resource() wrapper is provided for use in drivers.