QtPrivate::QSmartPointerConvertFunctor: Fix deprecation warning

Fix warning:
src/corelib/kernel/qmetatype.h:1723:27: warning: ‘T* QWeakPointer<T>::data() const [with T = QFile]’ is deprecated: Use toStrongRef() instead, and data() on the returned QSharedPointer [-Wdeprecated-declarations]

shown when compiling tst_QVariant by using
QWeakPointer::internalData().

Change-Id: I5ea543019b4f8e5dfc829939cd2011ae65f12876
Reviewed-by: Marc Mutz <marc.mutz@kdab.com>

src/corelib/kernel/qmetatype.h

@@ -1720,7 +1720,7 @@ namespace QtPrivate {
     {
         QObject* operator()(const QWeakPointer<T> &p) const
         {
-            return p.data();
+            return p.internalData();
         }
     };
 }

src/corelib/tools/qsharedpointer_impl.h

@@ -684,6 +684,7 @@ public:
     template<typename X>
     friend QPointer<X>
     qPointerFromVariant(const QVariant &variant);
+    friend QtPrivate::QSmartPointerConvertFunctor<QWeakPointer>;
 #endif
 
     template <class X>