QOpenGLPixelTransferOptions: declare as shared, add move assignment operator

A move constructor cannot be added because the class uses
a smart pointer to hold its pImpl, so the move ctor would
have to be out-of-line, destroying BC between C++11 and C++98
versions of Qt.

Member-swap is required for Q_DECLARED_SHARED, which in turn
enables efficient use of the class in Qt containers by marking
it movable.

Change-Id: I1aaa5bf3343a92e621d9464d8e4352f4e5ceff1f
Reviewed-by: Sean Harmer <sean.harmer@kdab.com>

src/gui/opengl/qopenglpixeltransferoptions.h

@@ -60,6 +60,14 @@ public:
     QOpenGLPixelTransferOptions &operator=(const QOpenGLPixelTransferOptions &);
     ~QOpenGLPixelTransferOptions();
 
+#ifdef Q_COMPILER_RVALUE_REFS
+    QOpenGLPixelTransferOptions &operator=(QOpenGLPixelTransferOptions &&other)
+    { swap(other); return *this; }
+#endif
+
+    void swap(QOpenGLPixelTransferOptions &other)
+    { data.swap(other.data); }
+
     void setAlignment(int alignment);
     int alignment() const;
 
@@ -88,6 +96,8 @@ private:
     QSharedDataPointer<QOpenGLPixelTransferOptionsData> data;
 };
 
+Q_DECLARE_SHARED(QOpenGLPixelTransferOptions)
+
 QT_END_NAMESPACE
 
 #endif // QT_NO_OPENGL