Remove ATSU-related dead code from wxOSX

ATSU was deprecated for a long time and was finally removed from OS X
SDK in 10.11. wxOSX_USE_ATSU_TEXT was unconditionally disabled already,
so the code was never used and can be safely removed.

include/wx/fontutil.h

@@ -158,21 +158,10 @@ public:
                   wxFontEncoding encoding);
 
     void Free();
-    void EnsureValid();
     
     static void UpdateNamesMap(const wxString& familyname, CTFontDescriptorRef descr);
     static void UpdateNamesMap(const wxString& familyname, CTFontRef font);
 
-    bool m_descriptorValid;
-
-#if wxOSX_USE_ATSU_TEXT
-    bool            m_atsuFontValid;
-    // the atsu font ID
-    wxUint32        m_atsuFontID;
-    // the qd styles that are not intrinsic to the font above
-    wxInt16         m_atsuAdditionalQDStyles;
-#endif
-
     int           m_pointSize;
     wxFontFamily  m_family;
     wxFontStyle   m_style;