Use the canonical bits for wired, etc. in the PTE. This is important for
interactions with certain kinds of hypervisors that look into the PTEs
more closely than they should.

Approved by:	re (kib)
Use a spin lock instead of a mutex to gate RTAS. This is required if RTAS
calls are involved in interrupt handling.

Approved by:	re (kib)
Add hook called when every new processor is brought online -- including the
BSP -- so that platform modules have a chance to add the new CPU to any
internal bookkeeping.

Approved by:	re (kib)
Add POWER CPUs to the kernel's knowledge. This does not imply we currently
actually run on any machines with POWER CPUs but avoids closing that door
unnecessarily.

Approved by:	re (kib)
Raise artificial limits on number of CPUs and number of interrupts.

Approved by:	re (kib)
Attach only on hardware that is actually supported as opposed to hardware
that seems like it has some of the problems we might want.

Approved by:	re (kib)