QDataStream: prevent accidental streaming of pointers

It doesn't make sense to stream a pointer, but it can happen by
accident because ds << ptr will select the operator<<(bool) overload.
Disable the out-stream operator for pointers by having a better match.

Reading a pointer from a QDataStream doesn't work, as a pointer
can't bind to e.g. a bool non-const reference.

[ChangeLog][QtCore][QDataStream] Streaming of arbitrary pointers
using QDataStream has been disabled. Note that such streaming happened
through the streaming operator for bool.

Change-Id: I4c98a33b52aae85e441f5a096efd404fbbf1e95f
Reviewed-by: Thiago Macieira <thiago.macieira@intel.com>

src/corelib/serialization/qdatastream.h

@@ -157,6 +157,7 @@ public:
     QDataStream &operator<<(const char *str);
     QDataStream &operator<<(char16_t c);
     QDataStream &operator<<(char32_t c);
+    QDataStream &operator<<(const volatile void *) = delete;
 
 
     QDataStream &readBytes(char *&, uint &len);