Re: diagnostics: prefer "…" to "..." if the locale supports it

[Paul Eggert]

>      diagnostics: prefer "…" to "..." if the locale supports it

Is this really a win? I normally used fixed-width fonts, and on my 
platform a string like "ABC…DEF" is all-too-easily confused with 
"ABC_DEF" if there are no underscores in the neighborhood. (I am using 
Fedora 30 with default fonts.)

For what it's worth, the Wikipedia manual of style 
<https://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style#Ellipses> says, 
"Wikipedia's style for an ellipsis is three unspaced dots (...); do not 
use the precomposed ellipsis character (…) or three dots separated by 
spaces (. . .)." Although Bison is not bound by any such style guide, 
I've found the Wikipedia style manual to be a good source for advice 
when trying to write clear documentation that is readable on the web.