compute_tree_correlations_matrix.scOU computes the (n+m)x(m+n) matrix of correlations
induced by the tree. It takes two cases in consideration: root fixed, or root in stationary
state.
compute_tree_correlations_matrix.scOU(times_shared, distances_phylo, params_old,
...)times of shared ancestry of all nodes and tips, result of function
compute_times_ca
(matrix) : phylogenetics distance, result of function
compute_dist_phy
(list) : old parameters to be used in the E step
matrix of variance covariance for the scOU