More Xen updates

Hi Ingo,

More patches.  There are three groups:

- some code movements to make common code available to other
  architectures (namely, ia64)
- Xen device driver updates, including a new xen paravirt framebuffer driver,
- The Xen balloon driver (shrink only, so no dependency on memory hotplug yet)
- some "using smp_processor_id while preemptable" warning fixes,
  mostly as a result of the core kernel's tendency to do tlb flushes
  and update init_mm while preemptable,
- other little Xen cleanups

Thanks,
	J