Mouse wheel release events?

[Po Lu]

Some mouse wheels generate special events when the user moves his finger
off the wheel, even if the wheel was not previously clicked.

These events are used by most applications to start inertial scrolling,
support for which I would like to add to Emacs.

I want to add a `wheel-release' event that is sent every time Emacs
receives such an event from the mouse wheel.  Is that okay?

Thanks.