cross_bicoherence() now follow an alternative
definition of (cross-)bicoherence due to Kim and Powers
(1979).
New function mode_matching() for fitting
cross-bicoherence’s empirical null distribution by the mode-matching
method of Schwartzman
(2008).
New function three_channel_mode() for generating a
simple example of multivariate time series.
New parameters mc and mc_cores of
bicoherence(), bispectrum(),
cross_bicoherence(), and cross_bispectrum()
for parallel computation.