add const qualifiers

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@52414 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/spinctrl.h

@@ -86,17 +86,17 @@ public:
     /**
         Gets maximal allowable value.
     */
-    int GetMax();
+    int GetMax() const;
 
     /**
         Gets minimal allowable value.
     */
-    int GetMin();
+    int GetMin() const;
 
     /**
         Gets the value of the spin control.
     */
-    int GetValue();
+    int GetValue() const;
 
     /**
         Sets range of allowable values.