folding.el vs isearch vs XEmacs 21.2+

There is a known bug with folding.el not entering folds when doing isearch on later version of XEmacs. I investigated the problem and it was triggered by the following change in XEmacs (isearch-mode.hack.el is a pached version of current XEmacs ispell with a portion replaced with code from XEmacs 21.1 ispell-mode.el). XEmacs switched to using overriding-local-map (presumable to sync with FSF). Here's a proposed patch. Note the comment, I tried to come up with a cleaner solution, but could not make it work. Any idea how to make this work cleanly? Otherwise, I think, this should be applied as is, since it improves functionality. Gleb