remove check for missing gtk_icon_size_lookup, since it is for GTK+ 2.1, and 2.4 is required now

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@50226 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/gtk/private.h

@@ -127,15 +127,6 @@ void wxRemoveGrab(wxWindow* window);
 // Escapes string so that it is valid Pango markup XML string:
 WXDLLIMPEXP_CORE wxString wxEscapeStringForPangoMarkup(const wxString& str);
 
-// The declaration for gtk_icon_size_lookup was accidentally ifdefed out in
-// GTK+ 2.1.0 which Sun seem to have shipped with some versions of JDS
-// for Solaris 9 x86.
-#ifdef NEED_GTK_ICON_SIZE_LOOKUP
-extern "C" gboolean gtk_icon_size_lookup  (GtkIconSize  size,
-                                           gint         *width,
-                                           gint         *height);
-#endif
-
 #ifdef __WXGTK20__
 #include <gdk/gdktypes.h>