bug#27122: 26.0.50; [PATCH] Add customizable to display unprintables as hex

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Robert Cochran <robert+Emacs@cochranmail.com> writes:

> IMO, this is the best solution. But the size that the ensuing discussion
> would inenvitably grow to puts me off of this path as well. I was
> initially thinking that the current behavior was more long-standing (10+
> years), but it was actually introduced in its current form in 2010, in
> d419e1d94 "Fix handling of 8-bit characters in a display table.".

While I'm also okay with changing this to hex display without an option,
I don't think that commit introduced the octal behaviour, it just
changed the implementation.  I think these these removed lines used to
do it:

-		    /* Insert three more glyphs into IT->ctl_chars for
-		       the octal display of the character.  */
-		    g = ((str[i] >> 6) & 7) + '0';
-		    XSETINT (it->ctl_chars[i * 4 + 1], g);
-		    g = ((str[i] >> 3) & 7) + '0';
-		    XSETINT (it->ctl_chars[i * 4 + 2], g);
-		    g = (str[i] & 7) + '0';
-		    XSETINT (it->ctl_chars[i * 4 + 3], g);