bug#12054: 24.1; regression? font-lock no-break-space with nil nobreak-char-display

[Drew Adams]

> > So just what is the "most general read syntax for a char" now?
> 
> The literal representation of the character.  This should 
> work on older Emacsen too, I think.  And on Emacs >= 22, you
> can use \uNNNN and \U00NNNNNN escape sequences if you like.

Got it.  So I guess there is no escape syntax that will work with older Emacs
versions also.  (You didn't say that, but I'm guessing.)

One problem with using a literal char is when you need the Lisp code to be
digestible by applications that choke on such chars.  That's one reason we
_have_ an escape syntax.

For example, uploading files containing certain control chars to certain sites
can result in them being filtered out.  Using escape syntax allows the actual
chars in the file to be ascii.

I understand that the \u and \U escape syntax fits the bill here, but not for
older Emacs versions.