Tweak the handling of PCI capabilities in emulated devices to remove
the non-standard zero capability list terminator.   Instead, track
the start and end of the most recently added capability and use that
to adjust the previous capability's next pointer when a capability is
added and to determine the range of config registers belonging to
PCI capability registers.

Reviewed by:	neel
A first pass at adding support for injecting hardware exceptions for
emulated instructions.
- Add helper routines to inject interrupt information for a hardware
  exception from the VM exit callback routines.
- Use the new routines to inject GP and UD exceptions for invalid
  operations when emulating the xsetbv instruction.
- Don't directly manipulate the entry interrupt info when a user event
  is injected.  Instead, store the event info in the vmx state and
  only apply it during a VM entry if a hardware exception or NMI is
  not already pending.
- While here, use HANDLED/UNHANDLED instead of 1/0 in a couple of
  routines.

Reviewed by:	neel