bug#47291: bug#51404: Support system dark mode on Windows 10

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: salvino@coderedcorp.com,  51404@debbugs.gnu.org,  47291@debbugs.gnu.org
> Date: Fri, 12 Nov 2021 04:00:18 +0100
> 
> > Maybe.  But some expert (which is not me) will have to explain what to
> > do when we receive these messages, or submit patches for that.
> 
> On the Linux side, we convert the messages to input events and then
> react to that event from special-event-map, which seems like a
> reasonable structure.

I mean how to tell what the message wants us to do, i.e. which parts
of the UI to change and in what way.