#include "unify.h"
int Need_Updates(int seg_id);
Need_Updates adds the calling worker process to the set
of worker processes that will receive updates when
Put_Updates(3) is called
with an argument of seg_id. The worker process can later
be removed from the copy set for a segment by calling Dont_Need_Updates(3).
On success Need_Updates returns 0. Otherwise, a value of -1
is returned.
Need_Updates can return an error if seg_id is
invalid.