2.4.2 const struct mpapi *mpapistop(int id);
API function for stopping mpolice and taking a delta snapshot, i.e..
all mpolice owned memory chunks allocated since last delta
id: a unique positive value for identifying this start/stop cycle
successful return:
  a pointer to a constant array of struct mpapi items
  the last item is empty and has addr==NULL, pbtrace==NULL, and size==0
error return: NULL (no current start, or current start not for id)
  1. the memory returned is owned by mpolice, do not try to write or free it.
  2. the memory returned will be reused on next successful stop call, do not
     keep references to that memory around for longer than that.