bug#40774: Error messages shouldn't be hidden when the user is idle

[ndame]

>
> My suggestion would instead be this:
>
> As an option (i.e. one can easily turn it off), have buffer `Messages' be 
> displayed on an idle timer.

This is not the same, because if there are progress messages too then errors
can be drowned in the noise, the user may not notice the error, and the user
usually doesn't care about progress message history.

It's much better if emacs collects the errors while the user is away and shows
them when the user is back, because if the computer can collect these then it
should do it instead of the user.

And when the user is back and sees the errors then he knows about them right
away without having to parse the Messages buffer visually.