Menu shortcut hiding has been removed

It had been causing problems in Unity for a while now and they
were missing on OSX as well in wx3.  So, the old menu Open/Close
method of hiding has been removed and replaced with an event
filter/monitor which looks for wxEVT_CHAR_HOOK events to pass
key events to the handler that has the keyboard captured.

src/AudacityApp.h

@@ -51,11 +51,6 @@ extern bool gIsQuitting;
 // Asynchronous open
 DECLARE_EXPORTED_EVENT_TYPE(AUDACITY_DLL_API, EVT_OPEN_AUDIO_FILE, -1);
 
-// Keyboard capture support
-DECLARE_EXPORTED_EVENT_TYPE(AUDACITY_DLL_API, EVT_CAPTURE_KEYBOARD, -1);
-DECLARE_EXPORTED_EVENT_TYPE(AUDACITY_DLL_API, EVT_RELEASE_KEYBOARD, -1);
-DECLARE_EXPORTED_EVENT_TYPE(AUDACITY_DLL_API, EVT_CAPTURE_KEY, -1);
-
 // Flags used in command handling.
 
 // These flags represent the majority of the states that affect
@@ -108,9 +103,7 @@ class AudacityApp:public wxApp {
    virtual int OnExit(void);
    virtual void OnFatalException();
 
-#if defined(__WXGTK__)
    int FilterEvent(wxEvent & event);
-#endif
 
    void InitLang( const wxString & lang );
 
@@ -207,12 +200,6 @@ class AudacityApp:public wxApp {
    void GenerateCrashReport(wxDebugReport::Context ctx);
 #endif
 
-#if defined(__WXGTK__)
-   /** \brief This flag is set true when in a keyboard event handler.
-    * Used to work around a hang issue with ibus (bug 154) */
-   bool inKbdHandler;
-#endif
-
  private:
    CommandHandler *mCmdHandler;
    FileHistory *mRecentFiles;