bug#26396: 25.1; char-displayable-p on a latin1 tty

[Eli Zaretskii]

> Date: Mon, 10 Apr 2017 10:05:01 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 26396@debbugs.gnu.org
> 
> Paul, could you please look into this?  I think the code in
> char-displayable-p which looks at the result of internal-char-font
> should only accept a non-negative value if the terminal-coding-system
> supports the character.  IOW, the Linux console should not be
> considered as being able to display a character unless the terminal
> encoding can safely encode it.

Or maybe the result of internal-char-font should be accepted only if
the terminal encoding is UTF-8 or some other Unicode encoding.