This is almost one year of changes to EXWM. Note that it undoes our
port of https://github.com/ch11ng/exwm/pull/737
That PR hasn't seen any movement in three years, so it might not be
that relevant anymore. Other stuff has been mainlined in the meantime.
Change-Id: I0845ff8a28a5bb1553855f6d6f0ceeaedcf0809e