Group-agnostic previous-focussed-window memory in StumpWM
I’ve started using StumpWM’s groups (like “workspaces” in other window managers) more extensively, but this broke a behaviour I like: the ability to easily switch back to the last focussed window, because StumpWM’s “last focussed” is group-specific. So I wasn’t easily about to switch quickly back and forth between two windows that were inb different groups, which turns out to be something I frequently want to do (e.g. switch back and forth between an emacsclient frame in my “emacs” group and a Firefox instance in my “web” group).