qdev/prop: macros for creating typechecked properties.

There are DEFINE_PROP_$TYPE("name", struct, field, default) macros for
each property type.  These macros link the qdev_prop_$name struct to the
type used by that property.  typeof(struct->field) is verifyed to be the
correct one for the given property.

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