Use override keyword

src/collectionattribute.h

@@ -59,7 +59,7 @@ public:
     /** Assignment operator. */
     CollectionAttribute &operator=(const CollectionAttribute &other);
 
-    virtual ~CollectionAttribute();
+    ~CollectionAttribute() override;
 
     /** Return whether the collection is enabled for a specified alarm type
      *  (active, archived, template or displaying).

src/compatibilityattribute.h

@@ -56,7 +56,7 @@ public:
     /** Assignment operator. */
     CompatibilityAttribute &operator=(const CompatibilityAttribute &other);
 
-    virtual ~CompatibilityAttribute();
+    ~CompatibilityAttribute() override;
 
     /** Return the compatibility status for the entity. */
     KACalendar::Compat compatibility() const;

src/eventattribute.h

@@ -55,7 +55,7 @@ public:
     /** Assignment operator. */
     EventAttribute &operator=(const EventAttribute &other);
 
-    virtual ~EventAttribute();
+    ~EventAttribute() override;
 
     /** Return the last command execution error for the item. */
     KAEvent::CmdErrType commandError() const;