Comment 9 for bug 390669

See attached branch, ready for merge.

Renamed file to match Martin Pitt's most recent commits. Added the description tag Martin added, and refreshed Mirco Muller's patch for 2.27.2. Keyboard brightness support had been dropped in 2.27.2, so that part of Mirco's original patch had been dropped along with the section:
/* display the widget when something else changed the backlight */
in brightness_changed_cb gpm-backlight.c since GPM no longer calls:
gpm_feedback_display_value (backlight->priv->feedback, (float) percentage / 100.0f);
in that function.