Implemented same functionality in mmq_2site_sq_dq_zq.
Problem, following system test fails!
test_korzhnev_2005_15n_dq_data
test_korzhnev_2005_15n_mq_data
test_korzhnev_2005_15n_sq_data
test_korzhnev_2005_1h_mq_data
test_korzhnev_2005_1h_sq_data
test_korzhnev_2005_all_data
test_korzhnev_2005_all_data_disp_speed_bug
Task #7807 (https://gna.org/task/index.php?7807): Speed-up of dispersion models for Clustered analysis.
