bug#11746: feature request: `isearch-query-replace' should open invisible text

[Juri Linkov]

>> > if you have `search-invisible' non-nil, isearch "opens" invisible
>> > text.  But when you hit M-% or C-M-% while searching, you loose this
>> > ability: point will just be put inside invisible areas, and you don't
>> > see what you're doing.
>>
>> The recent adaptation of isearch functions to `perform-replace'
>> makes it easy to implement this now.
>
> This sounds great.

Sorry for the delay, it required more testing with more fixes
like adding `isearch-clean-overlays' to `replace-dehighlight', etc.
This is installed now.