Add wxOVERRIDE and use it in common and wxOSX code.

Make overriding virtual methods more explicit and enable additional checks
provided by C++11 compilers when "override" is used.

Closes #16100.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@76173 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

src/html/m_layout.cpp

@@ -71,12 +71,12 @@ public:
 
     bool AdjustPagebreak(int* pagebreak,
                          const wxArrayInt& known_pagebreaks,
-                         int pageHeight) const;
+                         int pageHeight) const wxOVERRIDE;
 
     void Draw(wxDC& WXUNUSED(dc),
               int WXUNUSED(x), int WXUNUSED(y),
               int WXUNUSED(view_y1), int WXUNUSED(view_y2),
-              wxHtmlRenderingInfo& WXUNUSED(info)) {}
+              wxHtmlRenderingInfo& WXUNUSED(info)) wxOVERRIDE {}
 
 private:
     wxDECLARE_NO_COPY_CLASS(wxHtmlPageBreakCell);