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/common/cshelp.cpp

@@ -52,7 +52,7 @@ public:
         m_contextHelp = contextHelp;
     }
 
-    virtual bool ProcessEvent(wxEvent& event);
+    virtual bool ProcessEvent(wxEvent& event) wxOVERRIDE;
 
 //// Data
     wxContextHelp* m_contextHelp;
@@ -480,8 +480,8 @@ wxString wxContextId(int id)
 class wxHelpProviderModule : public wxModule
 {
 public:
-    bool OnInit();
-    void OnExit();
+    bool OnInit() wxOVERRIDE;
+    void OnExit() wxOVERRIDE;
 
 private:
     DECLARE_DYNAMIC_CLASS(wxHelpProviderModule)