bug#13052: 24.3.50; mention recent change of `kbd' to a function in NEWS

[Drew Adams]

> As for the `pure' property, it's now mentioned in the Lisp manual.

It is now mentioned, but this is all the manual says about it:

 This property is used internally to mark certain named functions
 for byte compiler optimization.  Do not set it.

Please explain why it is not appropriate for users to use this property on their
own functions.  That is not clear at all.

Why shouldn't a user function with a definition similar or even identical to
that for `kbd' have `pure' applied to it?  Especially since this apparently
affects only byte-compilation and has nothing to do with pure storage and
dumping Emacs.

What is your reason for declaring this off-limits for programmers of Emacs Lisp?
What good does that do?