bug#68698: 30.0.50; Making xt-mouse emit `wheel-up/down`

[Eli Zaretskii <eliz@gnu.org>]

> From: Stefan Monnier <monnier@iro.umontreal.ca>
> Cc: Eli Zaretskii <eliz@gnu.org>,  68698@debbugs.gnu.org
> Date: Thu, 25 Jan 2024 21:26:49 -0500
> 
> > A local run of HEAD (as of Jan 17, I'm at daec3e) with
> > "./configure --with-pgtk" has mouse-wheel-up-event set to wheel-down
> > because (featurep 'pgtk-win) is t, even with -nw on the command line.
> > Testing on Windows at Emacs 29.1 shows the same behavior.
> 
> This has been changed on `master` around Jan 19.  Now `mwheel.el` uses
> `wheel-up/down` unconditionally and `mouse-wheel-up/down-event` is only
> used for *other* events (defaults to `mouse-4/5`).

Was this reflected in the documentation?  The ELisp Reference manual
still says

     The ‘wheel-up’ and ‘wheel-down’ events are generated only on some
     kinds of systems.  On other systems, other events like ‘mouse-4’
     and ‘mouse-5’ are used instead.  Portable code should handle both
     ‘wheel-up’ and ‘wheel-down’ events as well as the events specified
     in the variables ‘mouse-wheel-up-event’ and
     ‘mouse-wheel-down-event’, defined in ‘mwheel.el’.  Beware that for
     historical reasons the ‘mouse-wheel-_up_-event’ is the variable
     that holds an event that should be handled similarly to
     ‘wheel-_down_’ and vice versa.

Is that still correct and accurate?  (And what about a similar issue
with wheel-left/right?).