filter: always init a delta smoothener for 10/10ms on trackpoints

If the trackpoint gives us deltas with less than 10ms intervals, something is wrong. Could be bad hardware, a glitch in the matrix or a discontinuity in the otherwise appropriately named time-space continuum. Usually it's the first.

Let's always set up trackpoint delta smoothening for 10ms to improve the pointer speed calculation and avoid jerky behaviors. i.e. if a trackpoint delta comes in below 10ms, pretend it came in with a 10ms interval for calculating the speed.

Fixes #104 (closed)