bug#22919: calc should use square root symbol to denote square root

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Cc: flexibeast@gmail.com,  zephyr.pellerin@gmail.com,  22919@debbugs.gnu.org
> Date: Tue, 08 Mar 2016 02:22:39 -0500
> 
> Eli Zaretskii wrote:
> 
> >> See eg ruler-mode-fill-column-char and how it uses char-displayable-p.
> >
> > That might not work well on a TTY, though.
> 
> In the sense that on a tty char-displayable-p may return nil when the
> answer is actually t? If so, I don't think that matters.
> Or vice versa?

The latter.  On a TTY, that function can only check whether the
terminal encoding supports the character, but it has no way of knowing
whether the terminal emulator will find a glyph in its font for the
particular character.