easier to use and more flexible.
* Change BUS_ADD_CHILD to take an order argument instead of a place.
* Define a partial ordering for isa devices so that sensitive devices are
probed before non-sensitive ones.
* Re-work the resource allocation code to use helper functions in subr_bus.c.
* Add simple isa interface for manipulating the resource ranges which can be
allocated and remove the code from isa_write_ivar() which was previously
used for this purpose.