Make some member functions const

interface/wx/layout.h

@@ -84,14 +84,14 @@ public:
     wxEdge GetMyEdge() const;
     void SetEdge(wxEdge which);
     void SetValue(int v);
-    int GetMargin();
+    int GetMargin() const;
     void SetMargin(int m);
     int GetValue() const;
     int GetPercent() const;
     int GetOtherEdge() const;
     bool GetDone() const;
     void SetDone(bool d);
-    wxRelationship GetRelationship();
+    wxRelationship GetRelationship() const;
     void SetRelationship(wxRelationship r);
 
     // Reset constraint if it mentions otherWin