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/statbmp.h

@@ -80,6 +80,7 @@ public:
     virtual long MSWWindowProc(WXUINT nMsg, WXWPARAM wParam, WXLPARAM lParam);
 
 protected:
+    virtual wxBorder GetDefaultBorder() const;
     virtual wxSize DoGetBestSize() const;
     virtual WXDWORD MSWGetStyle(long style, WXDWORD *exstyle) const;