bug#50929: [External] : bug#50929: Add slurp-sexp and barf-sexp

[Drew Adams]

> I use C-<left> and C-<right>, but alternatives I can think of are
> M-<left> and M-<right>, C-< and C-> or M-[ and M-].  The former two
> combinations are both bound to left- and right-word, and the latter two
> combination is unbound in emacs-lisp-mode.

FWIW -

I'd prefer that no default key bindings be sacrificed
for this.  This kind of editing is mostly appropriate
for use with "structured editing" modes that
automatically and always pair delimiters.  I think it
makes most sense for only such modes to bind keys for
such commands.