wxButton::GetDefaultSize() added for MSW and documented

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@2980 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/msw/button.h

@@ -49,6 +49,8 @@ public:
 
     virtual void SetDefault();
 
+    static wxSize GetDefaultSize();
+
     // implementation from now on
     virtual void Command(wxCommandEvent& event);
     virtual bool MSWCommand(WXUINT param, WXWORD id);