bug#21663: 25.0.50; isearch-edit-string dont resume multi isearches

[Juri Linkov <juri@linkov.net>]

> In previous patch (isearch_3.patch) the variables are not
> restored because they were bind to the same symbol name, and
> multi-isearch-end will set them to nil.

Thanks, it's a safer approach to restore them explicitly.

> In addition, multi-isearch-end need to be added again to
> isearch-mode-end-hook, otherwise, even after exiting with C-g, C-s will
> start a multisearch instead of a normal isearch in the current buffer.

To avoid the need to add multi-isearch-end to isearch-mode-end-hook,
you could try to restore saved variables before calling isearch-mode.
Then multi-isearch-setup called from isearch-mode should take care of
adding multi-isearch-end to isearch-mode-end-hook when necessary
variables are already restored, i.e. when you save the variable
multi-isearch-next-buffer-function instead of
multi-isearch-next-buffer-current-function.  But OTOH
multi-isearch-current-buffer still needs to be restored after
isearch-mode in the same place where you already added it in your patch.
This way restarting isearch will emulate binding local variables
multi-isearch-next-buffer-function and multi-isearch-buffer-list in
multi-isearch-buffers before starting multi-buffer search.