QtDBus: sweep Q_DECLARE_METATYPE → QT_DECL_METATYPE_EXTERN

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Can't backport to Qt 6.3 or 6.2 because this change introduces new
exported symbols.

Task-number: QTBUG-102206
Change-Id: Iae9d4017a984c845a76d0b9b088ad3e467fe1d54
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Reviewed-by: Mårten Nordheim <marten.nordheim@qt.io>

src/dbus/qdbusargument.cpp

@@ -58,6 +58,8 @@
 
 QT_BEGIN_NAMESPACE
 
+QT_IMPL_METATYPE_EXTERN(QDBusArgument)
+
 QDBusArgumentPrivate::~QDBusArgumentPrivate()
 {
     if (message)

src/dbus/qdbusargument.h

@@ -157,7 +157,7 @@ protected:
 Q_DECLARE_SHARED(QDBusArgument)
 
 QT_END_NAMESPACE
-Q_DECLARE_METATYPE(QDBusArgument)
+QT_DECL_METATYPE_EXTERN(QDBusArgument, Q_DBUS_EXPORT)
 QT_BEGIN_NAMESPACE
 
 template<typename T> inline T qdbus_cast(const QDBusArgument &arg)

src/dbus/qdbusintegrator.cpp

@@ -79,6 +79,8 @@
 
 QT_BEGIN_NAMESPACE
 
+QT_IMPL_METATYPE_EXTERN(QDBusSlotCache)
+
 // used with dbus_server_allocate_data_slot
 static dbus_int32_t server_slot = -1;
 

src/dbus/qdbusintegrator_p.h

@@ -169,7 +169,7 @@ public:
 
 QT_END_NAMESPACE
 
-Q_DECLARE_METATYPE(QDBusSlotCache)
+QT_DECL_METATYPE_EXTERN(QDBusSlotCache, Q_DBUS_EXPORT)
 
 #endif // QT_NO_DBUS
 #endif