bug#40671: [DOC] modify literal objects

[Paul Eggert]

On 5/16/20 10:02 PM, Michael Heerdegen wrote:
> you can modify a lot of objects in Emacs and that
> will cause trouble.  We surely don't want to call them all constant or
> not safely mutable or whatever.

We may not *want* to do that, but that's what we're doing now (with the two
classes currently documented as "mutable objects" and "objects that you should
not change"). And I don't see any easy way to change the documentation to draw
the line that we'd like to draw (namely, between "mutable objects" and "objects
that you cannot change") because that's not how Emacs works and changing Emacs's
behavior will be nontrivial.

At this point I suspect it'll be a better of our time to look into improving
Emacs's behavior in this area, and worry about documentation wording later.