Mark QSimplex{,Constraint} final, AnchorData non-copyable

These final touch-ups for CID 390828 make the code easier to
understand and safer, because more unsafe operations are now forbidden
(subclassing and copying).

Coverity-Id: 390828
Pick-to: 6.9 6.8 6.5
Change-Id: I2e43be71d8c3db59d95e69ec16c41c1547a2f180
Reviewed-by: Magdalena Stojek <magdalena.stojek@qt.io>
Reviewed-by: Mate Barany <mate.barany@qt.io>

src/widgets/graphicsview/qgraphicsanchorlayout_p.h

@@ -75,6 +75,8 @@ struct AnchorVertex
   Represents an edge (anchor) in the internal graph.
 */
 struct AnchorData : public QSimplexVariable {
+    Q_DISABLE_COPY_MOVE(AnchorData)
+
     enum Type {
         Normal = 0,
         Sequential,

src/widgets/graphicsview/qsimplex_p.h

@@ -43,8 +43,10 @@ struct QSimplexVariable
 
     Where (ci, Xi) are the pairs in "variables" and K the real "constant".
 */
-struct QSimplexConstraint
+struct QSimplexConstraint final
 {
+    Q_DISABLE_COPY_MOVE(QSimplexConstraint)
+
     QSimplexConstraint() : constant(0), ratio(Equal), artificial(nullptr) {}
 
     enum Ratio {
@@ -109,7 +111,7 @@ struct QSimplexConstraint
 #endif
 };
 
-class QSimplex
+class QSimplex final
 {
     Q_DISABLE_COPY_MOVE(QSimplex)
 public: