[crossfire] [patch] fix inconstency between on_same_map and get_rangevector

[Pippijn van Steenhoven]

Greetings,
while working on a script that would move an NPC, one bug was found in
common/map.c. A diff is supplied at the following URL:
http://data.plan9.de/adjacent.txt
Basically, it's get_nearest_player which calls can_detect_enemy which then
calls on_same_map and if that returns yes, it returns random crap.