Do not perform a synchronous DBus call to update the brightness in real
time when the slider move, because at least on some hardware the call
is slow, which leads to the UI bogging down and looking frozen.

To fix this, cap the update rate in response to slider motion.  This
makes the brightness apply slightly slower, but prevent most bogging
down (if the rate is well chosen, at least).

This reverts commit 1db4b409322e559a3d3a03677dd482a0613f3b29.

fix indentation in some files

find . \( -name '*.h' -o -name '*.c' \) -exec sed -i 's/[[:space:]]*$//' {} \;
find . \( -name '*.h' -o -name '*.c' \) -exec sed -i 's/\t*$//' {} \;