Merge remote-tracking branch 'sstabellini/xen-2012-10-03' into staging

* sstabellini/xen-2012-10-03:
  xen: Set the vram dirty when an error occur.
  exec, memory: Call to xen_modified_memory.
  exec: Introduce helper to set dirty flags.
  xen: Introduce xen_modified_memory.
  QMP, Introduce xen-set-global-dirty-log command.
  qemu/xen: Add 64 bits big bar support on qemu
  xen: Fix, no unplug of pt device by platform device.

diff --cc qapi-schema.json
Simple merge

diff --cc qmp-commands.hx
Simple merge