Delete QPlatformDragPrivate object in QPlatformDrag's destructor

Change-Id: Ib722df14123b24ca044f6e0846aa1435c7e0e201
Reviewed-by: Rohan McGovern <rohan.mcgovern@nokia.com>

src/gui/kernel/qplatformdrag_qpa.cpp

@@ -88,6 +88,7 @@ QPlatformDrag::QPlatformDrag() : d_ptr(new QPlatformDragPrivate)
 
 QPlatformDrag::~QPlatformDrag()
 {
+    delete d_ptr;
 }
 
 QDrag *QPlatformDrag::currentDrag() const

src/gui/kernel/qplatformdrag_qpa.h

@@ -100,6 +100,8 @@ public:
 
 private:
     QPlatformDragPrivate *d_ptr;
+
+    Q_DISABLE_COPY(QPlatformDrag)
 };
 
 QT_END_NAMESPACE