Whenever the speed changes, ease into it over the next 200 ms.

Whenever the speed changes, ease into it over the next 200 ms.

This causes a slight delay compared to the operator's wishes,
but that should hardly be visible, and it allows for somewhat
better behavior when we get very abrupt changes from the controller
(or the lock button suddenly is pressed) -- it's essentially
more of an interpolation. Even more importantly, it will allow us
to make a little trick to increase performance in the next patch
that would be somewhat more jerky without it.