Export QQuickListModel (marked private)

There are some things that are difficult to achieve without this one.
Export for the more intrepid developer.

Change-Id: I3918835f66b9aa773eb5f2f2c58fb82aecc4b446
Reviewed-by: Matthew Vogt <matthew.vogt@nokia.com>

src/qml/qml/qquicklistmodel_p.h

@@ -64,7 +64,7 @@ class QQuickListModelWorkerAgent;
 class ListModel;
 class ListLayout;
 
-class Q_AUTOTEST_EXPORT QQuickListModel : public QListModelInterface
+class Q_QML_PRIVATE_EXPORT QQuickListModel : public QListModelInterface
 {
     Q_OBJECT
     Q_PROPERTY(int count READ count NOTIFY countChanged)