Reduce memory usage of dynamic properties

The dynamic property variants are stored as QList<QVariant>, which unfortunately
results in QList to behave as array-list because of the size of QVariant. By storing
the variants in a vector directly we can eliminate the array-list element pointers.

Change-Id: I8736e1cf48b9fc97df3007df4a439b793933f346
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>

src/corelib/kernel/qobject_p.h

@@ -110,7 +110,7 @@ public:
         QVector<QObjectUserData *> userData;
     #endif
         QList<QByteArray> propertyNames;
-        QList<QVariant> propertyValues;
+        QVector<QVariant> propertyValues;
         QVector<int> runningTimers;
         QList<QPointer<QObject> > eventFilters;
         QString objectName;