Xpra: Ticket #2679: centralize text clipboard targets and translation

See ticket:2673#comment:4.

We translate some in the X11 clipboard, and others in the macos / win32 clipboard class. It's messy and brittle.



Sat, 23 Jan 2021 05:57:54 GMT - migration script:

this ticket has been moved to: https://github.com/Xpra-org/xpra/issues/2679