qHash overload for Q{Explicitly,}SharedDataPointer

Interestingly, before that patch this compiled fine:

  typedef Q{Explicitly,}SharedDataPointer<QSharedData> Ptr;
  Ptr p(new QSharedData);
  auto hash = qHash(p);

This was because both Q{Explicitly,}SharedDataPointer overload 'operator
bool()' => qHash(int) was accepted. This, however, doesn't make sense.

Someone should probably take care of applying the safe bool idiom to
these classes as well.

Change-Id: I8bb6b2aacaa6166da817a6f3847093fd20a05a67
Reviewed-by: Olivier Goffart <ogoffart@woboq.com>

src/corelib/tools/qshareddata.h

@@ -44,6 +44,7 @@
 
 #include <QtCore/qglobal.h>
 #include <QtCore/qatomic.h>
+#include <QtCore/qhash.h>
 
 QT_BEGIN_NAMESPACE
 
@@ -274,6 +275,17 @@ namespace std {
 }
 QT_BEGIN_NAMESPACE
 
+template <class T>
+Q_INLINE_TEMPLATE uint qHash(const QSharedDataPointer<T> &ptr, uint seed = 0)
+{
+    return qHash(ptr.data(), seed);
+}
+template <class T>
+Q_INLINE_TEMPLATE uint qHash(const QExplicitlySharedDataPointer<T> &ptr, uint seed = 0)
+{
+    return qHash(ptr.data(), seed);
+}
+
 template<typename T> Q_DECLARE_TYPEINFO_BODY(QSharedDataPointer<T>, Q_MOVABLE_TYPE);
 template<typename T> Q_DECLARE_TYPEINFO_BODY(QExplicitlySharedDataPointer<T>, Q_MOVABLE_TYPE);