ZOOM: use size_t for scan hit counts and str size

ZOOM: use size_t for scan hit counts and str size

Functions ZOOM_scanset_term and ZOOM_scanset_display_term have changed,
so that occ (hit count) and len (string length) are now of type size_t
pointer rather than int pointer. This is to be able to represent large
hit counts and to also just to use the proper type for string length
(strlen result).