This should be useful to keep in sync animations.
Think about a point, it moves in the window and you want to calculate angle and direction of its movement to draw a line, listening update event, this became easy / possible.
Added 'update' event to Fx.CSS
Including this would slow down all animations heavily.
This was my first thought, but the problem' still here. we can't sync animations 'cose every Fx instance has its own timer.
We need a solution.
1.3 uses a single timer