remove unneeded virtual destructors

include/iundo.h

@@ -32,8 +32,6 @@ class UndoMemento
 {
 public:
 	virtual void release() = 0;
-	virtual ~UndoMemento() {
-	}
 };
 
 class Undoable
@@ -41,16 +39,12 @@ class Undoable
 public:
 	virtual UndoMemento* exportState() const = 0;
 	virtual void importState( const UndoMemento* state ) = 0;
-	virtual ~Undoable() {
-	}
 };
 
 class UndoObserver
 {
 public:
 	virtual void save( Undoable* undoable ) = 0;
-	virtual ~UndoObserver() {
-	}
 };
 
 class UndoTracker
@@ -60,8 +54,6 @@ public:
 	virtual void begin() = 0;
 	virtual void undo() = 0;
 	virtual void redo() = 0;
-	virtual ~UndoTracker() {
-	}
 };
 
 class UndoSystem
@@ -82,9 +74,6 @@ public:
 
 	virtual void trackerAttach( UndoTracker& tracker ) = 0;
 	virtual void trackerDetach( UndoTracker& tracker ) = 0;
-
-	virtual ~UndoSystem() {
-	}
 };
 
 #include "modulesystem.h"