Xpra: Ticket #2720: handle _NET_RESTACK_WINDOW

Example found in #2718, not sure which application does this.

Only pagers are meant to use this, and they don't really make sense to use via xpra..

Wed, 08 Apr 2020 12:35:08 GMT - Antoine Martin: status changed

As of r26042, we log a more detailed message.

Sun, 12 Apr 2020 16:09:08 GMT - Antoine Martin: milestone changed

Thu, 08 Oct 2020 03:31:10 GMT - Antoine Martin: status changed; resolution set

Partial support in r27629.

Will follow up in #2896.

Sat, 23 Jan 2021 05:58:57 GMT - migration script:

this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2720