Arc editor : use QPropertyUndoCommand instead of ChangePartCommand

git-svn-id: svn+ssh://svn.tuxfamily.org/svnroot/qet/qet/trunk@4066 bfdf4180-ca20-0410-9c96-a3a8aa849046

sources/editor/rectangleeditor.h

@@ -17,10 +17,13 @@
 */
 #ifndef RECTANGLE_EDITOR_H
 #define RECTANGLE_EDITOR_H
-#include <QtWidgets>
+
 #include "elementitemeditor.h"
+
 class PartRectangle;
 class StyleEditor;
+class QDoubleSpinBox;
+
 /**
 	This class provides a widget to edit rectangles within the element editor.
 */