[PATCH] special handling for `iso-next-group' is needed

hello, I'm now playing with current (fresh from CVS) XEmacs 21.5 with Mule. The patch I was submitting more than year ago: http://list-archive.xemacs.org/xemacs-patches/200107/msg00090.html is still relevant and applies cleanly (with small fuzz factor). Currently XEmacs beeps and says "'iso-next-group' not defined" when switching keyboard layout. Everyone I know have something in effect of (global-set-key 'iso-next-group nil) but the solution in patch is more correct because it does not abort the isearch mode. Please, apply it to current beta or tell me why it is not needed. --alexm