Pull check_overload and check_retal_strength into fire.cc and mark as static
Pull do_transporter and unload_onto_alien_sector into load.cc and mark as static.  Get rid of unused use_popn function.
Pull mech_defend, mech_attack_people, and people_attack_mech into move.cc as static functions.
Remove unused MostAPs function
Pull prin_aimed_at, mk_expl_aimed_at, DispOrdersHeader and DispOrders into order.cc and marked them as static.