xfce4-session: support newer upower by an Arch patch

Tested.
upower: use newer version by default

Tested on KDE4, fixed with xfce, and was used with GNOME before.
CC @lethalman.

I did not test e19, as it won't build, probably due to #5392 @shlevy.
CC maintainer @matejc.

Also removed a forgotten unused patch.