Fix periodic lags caused by xbacklight
Fix periodic lags caused by xbacklight

Seems like some update broke/changed something that causes xbacklight
to produce a short screen freeze when called.
To work around this issue the brightness value from /sys is used for
polling.

mphe/dotfiles,mphe/dotfiles,mphe/dotfiles,mphe/dotfiles,mphe/dotfiles,mall0c/dotfiles,mphe/dotfiles,mall0c/dotfiles