bug#19208: replace-match unhelpful error message

[Paul Eggert]

This is not strictly a question of what one would say in English, as 
mathematical notation is typically a better choice for mathematical notions. For 
example, in C it's typically better to write sixteen as "16" rather than as "6 + 
10" even though the latter is closer to the original English.

If we wanted code to mimic English better, COBOL would be a good choice. (Or 
maybe Perl. :-) But the goal is to write readable code, not to imitate how 
Anglo-Saxons talked.