Quieten warning about uninitialized use of d pointer

We had this issue in Qt 4 before: Clang considers the use of d uninitialized
in the initializer list for d. This might or might not be legal, the clang
devs are divided on that topic. Let's just use a more common form and ignore
the issue language lawyers.

Change-Id: I3324255963a6d0f4a9057fe0d1d9ae868d3efef7
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/tools/qsharedpointer_impl.h

@@ -625,7 +625,7 @@ public:
 
 #ifndef QT_NO_QOBJECT
     template <class X>
-    inline QWeakPointer(X *ptr, bool) : d(ptr ? d->getAndRef(ptr) : 0), value(ptr)
+    inline QWeakPointer(X *ptr, bool) : d(ptr ? Data::getAndRef(ptr) : 0), value(ptr)
     { }
 #endif