QmlJS: Add refcounting to FakeMetaObjects.

Previously they were leaked when a qmldump or the C++ exported QML
type list updated.

Just deleting the previous FakeMetaObjects is not an option, as they
might still be used in a QmlObjectValue owned by an Engine.

Reviewed-by: Erik Verbruggen

src/libs/cplusplus/ModelManagerInterface.h

@@ -147,7 +147,7 @@ public:
 
     virtual void findMacroUsages(const CPlusPlus::Macro &macro) = 0;
 
-    virtual QList<LanguageUtils::FakeMetaObject *> exportedQmlObjects() const = 0;
+    virtual QList<LanguageUtils::FakeMetaObject::ConstPtr> exportedQmlObjects() const = 0;
 
 Q_SIGNALS:
     void documentUpdated(CPlusPlus::Document::Ptr doc);