bug#20780: 25.0.50; explain where to find skeletons in autotype info manual

[Nicolas Richard <youngfrog@members.fsf.org>]

I was trying to find a template/skeleton mechanism, and that leads to
(info "(emacs) Text") :
>    The “automatic typing” features may be useful when writing text.
> *note The Autotype Manual: (autotype)Top.

Following through to the autotype info page, I'm a bit disappointed
because the manual explains how skeletons can:
- accept input in section 1,
- be modified with prefix arguments in section 2,
- be called as abbrevs in section 3,
and we have to wait section 4 to read about a (quite scary,
IMO) way to define skeletons. I'm now convinced that it is in fact not
expected that the *user* writes her own skeletons. Is that right ?

If that is the case, I suggest to mention that fact right from the
beginning, and maybe explicitly list a few places where skeletons are
actually availables (which key). C-mode is mentionned but from "emacs -Q
-f c-mode" I couldn't find anything in the menu.

Nicolas.