Bug#574169: xserver-xorg-video-radeon: dims display after some days of uptime

[Piotr Engelking <inkerman42@gmail.com>]

I can reproduce this bug with xserver-xorg-video-radeon 1:6.12.192-1,
KMS-enabled upstream stable kernel 2.6.33.1, and xscreensaver 5.10-7
by running 'xscreensaver-command -lock' in X and switching to another
console before the screen finishes fading. (This requires the
xscreensaver 'fade' option to be enabled, which is on by default.)
After unlocking X, the screen is considerably dimmer. Running xgamma
results in the following output:

$ xgamma
-> Red  1.000, Green  1.000, Blue  1.000
$

Running 'xgamma -gamma 1' _does_ however result the screen to normal brightness.

This bug may very well not be radeon-related, but I am not able to
test it on another hardware at the moment - please do. (Cc-ing
xscreensaver maintainers.)