bug#20545: New minor mode Electric Punct

[Paul Eggert]

Eli Zaretskii wrote:

> The documentation patch says it's enabled by default.

It's enabled, but the variables that configure it make it inactive by default. 
I'll try to make this clearer in the documentation.

> I don't think we should enable this by default, not even in
> .dir-locals.el.

We can certainly hold off on the .dir-locals.el part for a bit, to see how it 
works for developers who want to try it.

> Do we already have a way of displaying ‘..’ on terminals that cannot
> display them (notably, some TTYs)?  If not, we should add that before
> we install these changes, and those in bug #20385.  I don't think we
> can let doc strings have glyphless characters.

I just now configured a terminal to refuse to display curved quotes, and when I 
used it Emacs displayed "‘like this’" as "\u2018like this\u2019" with 
underscores below the "\u2018" and the "\u2019".  I could easily change it to 
display it as "`like this'" with underscores under the "`" and the "'", if you 
think that'd be a win.