Tag forwarded X11 connection as remote

[Damien Miller]

On Mon, 2 Oct 2017, Michal Srb wrote:

> SSH only needs to change the first byte sent from X client to server
> to mark it as remote. SSH already modifies the whole first message
> (replaces authorization data), so changing the first byte is easy
> addition.
>
> I have attached patch that implements it. Please check it and consider
> adding it or something similar to openssh.

Thanks - is this flag fully backwards-compatible? Is there a chance it
could cause problems on older X11 implementations? IMO most of the people
using X11 forwarding are likely using it to/from older systems.

-d