compute_variance_covariance.scOU
computes the (n+m)*p squared variance covariance
matrix of vec(X).
compute_variance_covariance.scOU(times_shared, distances_phylo, params_old,
...)
times of shared ancestry of all nodes and tips, result of function
compute_times_ca
(matrix) : phylogenetic distance, result of function
compute_dist_phy
(list) : old parameters to be used in the E step
matrix of variance covariance for the scOU