Add a clock observation to the internal slaving algorithm the same as Clock.addObservation, and return the result of the master clock estimation, without updating the internal calibration.
The caller can then take the results and call Clock.setCalibration with the values, or some modified version of them.
a time on the slave
a time on the master
a pointer to hold the result
a location to store the internal time
a location to store the external time
a location to store the rate numerator
a location to store the rate denominator