Re: multiple displays and ttys

[Richard Stallman]

    I suggest the patch below which makes that only the frames on
    the `current terminal' are considered as visible.

It seems logical, for most purposes.  But I think it would be a good
idea to check the calls to the principal primitives that loop over
windows, to see which calls specify visible windows only, and check if
this is right for all of them.  It is probably right for most of them;
what I am not sure of is whether it is right for all of them.

We might want to make the arguments which traditionally mean "visible
frames" now mean "visible on this terminal", and create some other way
to say "visible on any terminal" -- if the latter is really needed.
But if it isn't needed, we are better off keeping things simple
and not creating it.