implemented GetDefaultBorder() in wxControl, override it in some controls which don't want to have sunken style by default

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@21719 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/stattext.h

@@ -46,6 +46,7 @@ public:
 
 protected:
     // implement/override some base class virtuals
+    virtual wxBorder GetDefaultBorder() const;
     virtual void DoSetSize(int x, int y, int w, int h,
                            int sizeFlags = wxSIZE_AUTO);
     virtual wxSize DoGetBestSize() const;