Reapply 403343039d on 5.11

This change amends 305dd1b61f, which lost
40334303 and brought src/corelib/xml/qxmlstream_p.h back. In
a6b697ca13, it was moved to
src/corelib/serialization/qxmlstream_p.h in 5.11.

Change-Id: Ia1e9841b866ff49f7274b1b13fd224c0a20a017e
Reviewed-by: Ville Voutilainen <ville.voutilainen@qt.io>
Reviewed-by: Friedemann Kleint <Friedemann.Kleint@qt.io>

src/corelib/serialization/qxmlstream_p.h

@@ -651,7 +651,8 @@ public:
     inline void reserve(int extraCapacity) {
         if (tos + extraCapacity + 1 > cap) {
             cap = qMax(tos + extraCapacity + 1, cap << 1 );
-            data = reinterpret_cast<T *>(realloc(data, cap * sizeof(T)));
+            void *ptr = realloc(static_cast<void *>(data), cap * sizeof(T));
+            data = reinterpret_cast<T *>(ptr);
             Q_CHECK_PTR(data);
         }
     }