Windows in workspace.clientList() are sorted in the map order. This
means that the minimize all script will try to activate the last mapped
window when unminimizing windows, which is a bit annoying.

This change ensures that the minimize all script doesn't activate wrong
window by minimizing and unminimizing windows in the stacking order.
It's not a bullet-proof solution though, but it should produce good
enough results.


(cherry picked from commit 22b7ac02)