bug#33199: lambda forms are not self-quoting

[Eli Zaretskii <eliz@gnu.org>]

> From: Noam Postavsky <npostavs@gmail.com>
> Date: Mon, 29 Oct 2018 19:06:25 -0400
> Cc: garreau@debbugs.gnu.org, alexandre <galex-713@galex-713.eu>
> 
> Alexandre's recent post about pcase-lambda made me notice that lambda's
> docstring claims lambda forms are self-quoting.  However, they are not:
> 
>     ;; -*- lexical-binding: t -*-
>     (setq lexical-binding t) ; for *scratch*
> 
>     (lambda (x) (+ 1 x)) ;=> (closure (t) (x) (+ 1 x))

The doc string is still correct if lexical-binding is not in effect,
isn't it?

> From: Noam Postavsky <npostavs@gmail.com>
> Date: Mon, 29 Oct 2018 19:01:07 -0400
> Subject: [PATCH v1] Don't claim lambda forms are self-quoting
> 
> * doc/lispref/functions.texi (Anonymous Functions):
> * lisp/subr.el (lambda): Don't say that a lambda form yields itself,
> under lexical binding it yields a closure object.

This removes useful information, IMO.  I'd be much happier if we added
to the existing docs that lambda is not self-quoting in the
lexical-binding environment, and described (and explained) what does
happen in the lexical-binding environment.

Thanks.