Add opening symbols to clones of windows

The method execute must create the sshapes and vshapes objects. They must
1. exist in the cloned (parent) object (by calling the execute function)
2. and be copied to the clone object.
Then the SVG rendering in ArchSectionPlan can find it.

src/Mod/Arch/ArchWindow.py

@@ -697,6 +697,13 @@ def onChanged(self,obj,prop):
     def execute(self,obj):
 
         if self.clone(obj):
+            clonedProxy = obj.CloneOf.Proxy
+            if not (hasattr(clonedProxy, "sshapes") and hasattr(clonedProxy, "vshapes")):
+                clonedProxy.execute(obj.CloneOf)
+            self.sshapes = clonedProxy.sshapes
+            self.vshapes = clonedProxy.vshapes
+            if hasattr(clonedProxy, "boxes"):
+                self.boxes = clonedProxy.boxes
             return
 
         import Part,DraftGeomUtils,math