bug#41445: 26.3; Query-replace triggers "match data clobbered by..."

[Drew Adams]

>     NOTE: The convention in Elisp is that any function, except for a
>     few exceptions like car/assoc/+/goto-char, can clobber the match
>     data, so `save-match-data' should normally be used to save *your* 
>     match data rather than your caller's match data.

+1.  I like that, especially the last phrase.
Clear; important to get across.