bug#16035: 24.3.50; Custom isearch broken on trunk (e.g. change-log-mode)

[Juri Linkov]

> Case 2:
>
> isearch in the popular third-part package "folding" is broken, same
> symptoms as above. (If you don't have it I can supply a copy.)
>
>     ./nextstep/Emacs.app/Contents/MacOS/Emacs -Q folding.el -l folding.el
>     y
>     M-x folding-mode RET
>     C-s defvar
>     C-a

folding.el performs such initialization in `folding-isearch-hook-function':

          (funcall (symbol-function 'set)
                   'overriding-terminal-local-map folding-isearch-mode-map)

and this condition in `isearch-pre-command-hook' fails:

     ((not (eq overriding-terminal-local-map isearch-mode-map)))

Maybe this condition should be checked only when handling a scrolling function
or prefix argument like in the patch that I posted in bug#15568.