// Makes zone_b adjacent to zone_a.  If one_way is false, zone_a is also made "adjacent" to zone_b
// Note that you may not always want zombies coming from zone B while you are in Zone A, but you 
// might want them to come from B while in A.  It's a rare case though, such as a one-way traversal.

add_adjacent_zone( zone_name_a, zone_name_b, flag_name, one_way, zone_tag_a, zone_tag_b )