Smooth deceleration support has been added to ZProbe.cpp. (It already had smooth ACCELERATION, but the deceleration was just an immediate, jerking stop that encourages step loss.) If your probe can tolerate being moved one or two millimeters beyond the point at which it triggers, this is a great option to turn on! However, the default is for it to be off, because some probes may not work well with that and I don't want to stress anything.

Need evidence? Sure! With a sample size of 30, a simple repetitive depth probe returned a range of 8 steps (2.245 standard deviations) without smooth decel, and 4 steps (1.284 standard deviations) with smooth decel.

Also, added some methods for getting and setting more variables (debounce, feedrate, smooth decel) so that my delta strategy can modify them without having to edit a file and reset the controller.
Added capability to store and retrieve the system acceleration setting. The strategy now drops the acceleration to a nice low value in order to ensure smoothness of probing (only in measure_probe_repeatability() so far, but other methods will follow.)

Added some more options to measure_probe_repeatability(). It can now directly modify the following from G-code: Acceleration, debounce count, smooth deceleration, eccentricity test, probe smoothing, fast and slow feedrates, and number of samples.