Adding wxMac accessibility. Should resolve:

http://bugzilla.audacityteam.org/show_bug.cgi?id=139

src/MixerBoard.h

@@ -49,6 +49,9 @@ public:
 
    void OnMouseEvent(wxMouseEvent & event);
 
+   void OnFocus(wxFocusEvent &event);
+   void OnCaptureKey(wxCommandEvent& event);
+
 protected:
    bool mIsPan;
 
@@ -108,6 +111,7 @@ private:
    void OnButton_Solo(wxCommandEvent& event);
    //v void OnSliderScroll_Gain(wxScrollEvent& event);
 
+
 public:
 #ifdef EXPERIMENTAL_MIDI_OUT
    // mTrack is redundant, but simplifies code that operates on either