pc: Move PCMachineClass, PCMachineState to qemu/typedefs.h They will be used inside hw/xen/xen.h, which doesn't include hw/i386/pc.h. Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>