[C (pkgs/locale)] Fix -help in Japanese UTF-8 setups

APPROVE Technically, you could use (fboundp 'char-to-unicode) or something like that which is specific to the Unicode support which started in 21.5.8 or so. But your version test is a lot easier to understand. > The attached patch crudely fixes it. Unless someone objects or comes > up with a better way to fix it, will apply in a couple of days. > > 2007-05-08 Ville Skyttä <scop(a)xemacs.org&gt; > > * start-files/ja/locale-start.el (command-line-do-help): > Don't try to load `un-define' with XEmacs >= 21.5.