bug#15917: 24.3.50; manual: mention keys reserved for users

[Stefan Kangas]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Eli Zaretskii <eliz@gnu.org> writes:
>
>> That'd be fine with me, but should we perhaps clarify what is a
>> "letter" in this context?  Are we talking about ASCII letters only, or
>> are non-ASCII letters also included?
>
> Good question.  I assumed that this was about ASCII letters only, but
> thinking about it, I don't see why: I think we should reserve all `C-c
> LETTER' key sequences for the users.

Agreed.  OTOH, it would be pretty odd for Emacs or any packages to bind
non-ASCII letters.  I've never seen any software bind such keys by
default, I think.

But if we do add it, we should probably update `(elisp) Key Binding
Conventions' as well.