Store only up to MAXPRCON constituents, not MAXCHRNV; code doesn't
fully support more than three anyway. Remove member p_nv, use item
type I_NONE for unused slots. Rename members p_vtype, p_vamt to
p_ctype, p_camt to avoid confusion with variable-style storage.
(pchr): Initializers adapted.
(nullify_objects, materials_cost, materials_charge, prod,
show_sect_capab, grind): Adapt, simplify where possible, protect
against bad item types in pchr[].
(MAXCHRNV): Unused, remove.
constituents in sector. Work directly on item arrays instead of
copies made by getvec(). This is safe, because the old code made
single copies and always flushed them back into the unit structures
before flushing those.
