suspend: switch acpi s3 to new infrastructure.

This patch switches pc s3 suspend over to the new infrastructure.
The cmos_s3 qemu_irq is killed, the new notifier is used instead.
The xen hack goes away with that too, the hypercall can simply be
done in a notifier function now.

This patch also makes the guest actually stay suspended instead
of leaving suspend instantly, so it is useful for more than just
testing whenever the suspend/resume cycle actually works.

Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
