libbacklight support for randr backlight property

[Dave Airlie]

xbacklight and gnome would really like to use xrandr to control the backlight
if possible, I've just taken the property code from intel driver, and hooked
it up to libbacklight from git://git.freedesktop.org/git/libbacklight.

The kernel can't deal with this due to the insanity that is ACPI and non-ACPI
backlight controls, so lets just hope this works instead!

I've only tested this on my T60p ancient piece of crap, appreciate any testing
anyone can give it.

Dave.