Now that the GUI is more prominent (#1762), users are more likely to use xpra mdns-gui to browse for sessions.
This works well on all platforms we package for except on win32.
We cannot bundle bonjour for windows (non-free license), but we can at least tell the user that support is missing and give them a link to the download page.
Done in r20692.
this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/1989