bug#21684: 25.0.50; undo in query-replace w/o exit

[Tino Calancha]

> I wonder why it's harder to implement for regexps?
Basically for my lack of expertise in this code: i was trying
to extend my patch to support regexp without success.

> you could add all previous replacements strings
> to the same stack at the end of data elements
> like we did when necessary by adding new data at
> the end of the similar isearch stack elements in isearch-cmds.
Thank you, it sounds a good idea!!

See new patch (replace-2.patch): AFAICS is working as i wanted.
Please try it and feel free to give me any comments if you
find some issues to fix/improve.

replace-2.patch
Description: Text document