backlight_helper_get_best_backlight()

[Jack Bates]

Power Manager fails to control the actual brightness of my laptop
(Eee PC 1201N) for basically the same reason as here:
http://forum.xfce.org/viewtopic.php?id=9547

Would you consider a patch to replace the list in 
backlight_helper_get_best_backlight()
http://git.xfce.org/xfce/xfce4-power-manager/tree/src/xfpm-backlight-helper.c#n384

with the same logic as here:
https://git.gnome.org/browse/gnome-settings-daemon/tree/plugins/power/gsd-backlight-linux.c#n61

i.e. grab the first interface of type "firmware" and fall back on the 
first interface of type "platform" and finally "raw".