number of samples per waveform will be altered by this function when 
     samples are made invalid by realignment (i.e., the amount of shift requires
     extrapolating past the boundaries of the original waveform) and the returned
     SPIKES object will have its waveforms clipped to exclude invalid regions.
     The MAXSHIFT argument limits this by specifying the maximum allowed shift
     (in samples).  Waveforms requiring more than a MAXSHIFT samples realignment
     are taken to be outliers and will n