bug#7524: 24.0.50; backquote converts newlines in strings to "\n"

[Drew Adams]

> And yes, Custom should probably try to wrap lines somehow in 
> such cases (e.g. pretty-print the sexp).

Any chance this pretty-printing will actually get done?
The utility goes well beyond `\n' in strings.

Just now I created a defcustom whose :type is
(repeat (restricted-sexp
         :tag "Keymap"
         :match-alternatives (keymapp 'nil)))

And you cannot believe how ugly such a value is, not to mention how error-prone
editing it would be!  Regardless of what one might think of trying to use a
keymap value this way, the point is that any non-trivial Lisp sexp needs to be
pretty-printed.

`restricted-sexp can be a quick-and-dirty substitute for defining the widgets
needed to get a new :type construct.  But it is rendered pretty unusable without
(at least) pretty-printing.

There are likely to be plenty of Lisp values for which pretty-printing would
help.  Any chance you will add this to the Emacs TO-DO list?