QDBusMessage: declare as shared-come-Qt6

Requires adding member-swap and (at least in my copy) move assignment.

Since the type does not contain a d == nullptr state,
a move constructor isn't yet possible.

Change-Id: Iad6939fa30f214591eab1fdf30a2cf1423ffb32a
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/dbus/qdbusmessage.h

@@ -62,9 +62,14 @@ public:
 
     QDBusMessage();
     QDBusMessage(const QDBusMessage &other);
+#ifdef Q_COMPILER_RVALUE_REFS
+    QDBusMessage &operator=(QDBusMessage &&other) Q_DECL_NOTHROW { swap(other); return *this; }
+#endif
     QDBusMessage &operator=(const QDBusMessage &other);
     ~QDBusMessage();
 
+    void swap(QDBusMessage &other) Q_DECL_NOTHROW { qSwap(d_ptr, other.d_ptr); }
+
     static QDBusMessage createSignal(const QString &path, const QString &interface,
                                      const QString &name);
     static QDBusMessage createTargetedSignal(const QString &service, const QString &path,
@@ -117,6 +122,7 @@ private:
     friend class QDBusMessagePrivate;
     QDBusMessagePrivate *d_ptr;
 };
+Q_DECLARE_SHARED_NOT_MOVABLE_UNTIL_QT6(QDBusMessage)
 
 #ifndef QT_NO_DEBUG_STREAM
 Q_DBUS_EXPORT QDebug operator<<(QDebug, const QDBusMessage &);