Implement wxButton::SetDefault to call SetDefaultItem on the top-level window.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/branches/WX_2_8_BRANCH@48529 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/cocoa/button.h

@@ -59,6 +59,7 @@ public:
     wxString GetLabel() const;
     void SetLabel(const wxString& label);
     wxSize DoGetBestSize() const;
+    virtual void SetDefault();
 };
 
 #endif