bug#48148: 27.2; ox-ascii breaks TITLE line wrongly when 2 width char is used

[Eli Zaretskii]

> From: Nicolas Goaziou <mail@nicolasgoaziou.fr>
> Cc: shingo.fg8@gmail.com,  48148-done@debbugs.gnu.org
> Date: Sun, 02 May 2021 17:56:04 +0200
> 
> More than the width of the text, I'm interested in the
> ratio between the width of the text and the width of an underline
> character (assuming monospace).

And that is rarely 2 for double-width characters.  Especially if the
underline and the double-width characters are displayed using
different fonts.

> The string may not be displayed at all. Since it is the output of an
> export process, it could, e.g., be written to a file.

If that text file can be displayed using some software you know
nothing about, then this problem doesn't have an accurate solution,
only approximate ones.