anchor.diff:  Get the total number of observations so far made.
   
   If the distribution is `NULL`, then return `0`.
  +
  +*Examples:*
  +[source,c]
  +----
  +inform_dist *dist = NULL;
  +assert(inform_dist_counts(dist) == 0);
  +----
  +[source,c]
  +----
  +inform_dist *dist = inform_dist_uniform(5);
  +assert(dist);
  +assert(inform_dist_counts(dist) == 5);
  +inform_dist_set(dist,2) = 4;
  +inform_dist_set(dist,3) = 3;
  +assert(inform_dist_counts(dist) == 10);
  +inform_dist_free(dist);
  +----
   ****
   
   ****
  
positive.code: Get the size of the distribution's support.
  
  If the distribution is `NULL`, then a support of `0` is returned.
  ****
  
  ****
  
negative.code: distribution.
  ****
  
  [[dist-allocation]]
  == Allocation
  ****
  [[inform_dist_alloc]]
  [source,c]
  