Remove remaining unused carbon implementation code.

Remove code and files which should have already been removed in 5ba67c67e4.

include/wx/osx/glcanvas.h

@@ -161,13 +161,6 @@ protected:
     WXGLPixelFormat m_glFormat;
     wxGLAttributes m_GLAttrs;
 
-#if wxOSX_USE_CARBON
-    bool m_macCanvasIsShown,
-         m_needsUpdate;
-    WXGLContext m_dummyContext;
-    GLint m_bufferName;
-#endif
-
     wxDECLARE_EVENT_TABLE();
     wxDECLARE_CLASS(wxGLCanvas);
 };