bug#25794: 24.5; Doc of `Info-selection-hook'

[Eli Zaretskii]

> Date: Sun, 19 Feb 2017 09:28:27 -0800 (PST)
> From: Drew Adams <drew.adams@oracle.com>
> 
> This is a hook: a variable used by users to automatically invoke
> functions when something happens.
> 
> Sure, it's true that "when something happens" means, more precisely, at
> certain places in the implementation (code).  But a hook is a user-level
> thing, and hooks should be, first of all, presented to users as such.
> Their descriptions should make clear to users when they are used.
> 
> That's not really the case for `Info-selection-hook', IMO.  Why?
> Because users do not know what "when `Info-select-node' is called"
> means.  They know nothing about non-interactive function
> `Info-select-node'.
> 
> (Also, the doc string says "Hooks run" - that should be singular.)

Fixed on the emacs-25 branch.

Thanks.