bug#40671: [DOC] modify literal objects

[Michael Heerdegen]

Hello Paul,

I had a quick look at your changes.  I agree that it would have been
better to discuss before you start to install what you think you like.

Some things add more confusion.  Before your changes the manual used the
term "literal" objects, now you added a different wording "constant"
vs. "mutable" that describes more or less the same thing.

Then some things you added are just wrong, at least in the generality
you word them.  As Drew said, `quote' doesn't always return constant
objects, the special form just returns the OBJECT, whatever it is, when
it is evaluated.

Or:

|  Vectors written with square brackets are constants and should not be
|  modified via @code{aset} or other destructive operations.

(let ((l (list 1 2 3)))
  (let ((my-vector `[,@l]))
    my-vector))

What does this sentence tell me about the vector I constructed?

We should really be super careful with these changes.

Michael.