bug#10844: 24.0.93; Slightly unclear help text about remapped commands

[Drew Adams]

> kill-buffer is an interactive built-in function in `C source code'.
> It is remapped to `ido-kill-buffer', which is bound to C-x k.
> 
> I was puzzled [by] what this meant.

Remapping: the "mapping" is between commands and keys.  It should be sufficient
to add only a couple of words here to make things clearer.  E.g.

Its keys have been remapped to `ido-kill-buffer': `C-x k', `C-M-whatever',...
^^^^^^^^

It is fine for the regular doc, which explains things more precisely and at more
length, to speak of one _command_ being remapped to another _command_.  But here
it might be better to speak of one command's key bindings being remapped to
another command.

That said, I don't have a problem with the current help in this context.  I
mainly want us to avoid becoming verbose here just in order to make clear what
admittedly could be confusing.