MaxDisplays configuration option

[AG]

>
> From decades in the field, I'd say It's pretty weird. I've not
> personally seen anything approaching that number of clients on a
> single server in..... well, not since I worked with Multics back in
> the 1980's. Dozens on a robust system, yes. One thousand?

>> We do have some boxes with concurrent ssh-users in the lower 3-digit
>> range. But in general this seems to be rare, especially since software
>> is often unprepared for and untested in that amount of activity (see
>> e.g. https://github.com/systemd/systemd/issues/1961).
>>
>> For the number of X displays, there was never any issue, usually since
>> CPU and memory resources run out long before you run out of display
>> numbers. Users just pick another box or their laptop, if applications
>> are slow, so the number of X displays is self-limiting ;)
>>
>>
>>
>> Ciao,
>>
>> Alexander Wuerstlein.

I should clarify, these aren't systems that have users shell access to.
It's an X11 forward only, used as a chokepoint into a segregated network.

Anyway, I will clean up the patch and add documentation and then report
back. I've already created an entry on the bugtracker in case anyone wants
to follow along.

https://bugzilla.mindrot.org/show_bug.cgi?id=2580

Thx,
A