ad_disc_set_PreferredDC
(void) ad_disc_set_PreferredDC(ad_ctx,
(void) ad_disc_set_PreferredDC(ad_ctx, NULL);
(void) ad_disc_set_PreferredDC(ad_ctx,
(void) ad_disc_set_PreferredDC(ad_ctx,
(void) ad_disc_set_PreferredDC(ad_ctx, NULL);
ad_disc_set_PreferredDC(ad_disc_t ctx, const ad_disc_ds_t *dc);