winner-undo breaks perspectives

[KaratasFurkan]

When I switch from perspective A to perspective B and run winner-undo, window layout of B becomes same with A.

[gcv]

Yes, I know. Definitely worth fixing.

I think it can be done by advising the winner-ring function and changing winner rings to key on frame+perspective pairs, rather than just frames. The current perspective would be the one always used (I hope that's not too much of a limitation). Unfortunately, it looks like winner-ring is defined using defsubst instead of defun, so I'm not sure if Elisp advice will work on it.