Add Q_OBJECT_BINDABLE_PROPERTY() macro that can be used to define
a bindable property inside QObject.
The macro and the class behind it creates storage for a property
that is bindable inside a QObject or QObjectPrivate. The property
only uses as much space as the data contained, ie. it has no
storage overhead, as long as no bindings are being used.
Bindings are being stored and looked up in the QBindingStorage
associated with the owning object.
Change-Id: I1dadd7bddbad6fbf10cfa791d6461574b9db82dd
Reviewed-by: Volker Hilsheimer <volker.hilsheimer@qt.io>
3b3b190eef