changes for some sub-functions in dirac_dec_render_sf

[x] changes for ivas_dirac_dec_compute_directional_responses and its sub-functions
[x] changes for ivas_dirac_dec_compute_gain_factors
[x] changes for ivas_dirac_dec_compute_power_factors

[x] Basops and instrumentation code added.
[x] intermediate conversions inside functions cleaned up.
[x] pending: integration of mvr2r_inc function in ivas_dirac_dec_compute_directional_responses.