[crossfire] NPC recursive bug

[Nicolas Weeger (Laposte)]

Hello.

Related to bug: 
https://sourceforge.net/tracker/index.php?func=detail&aid=1534889&group_id=13833&atid=113833

I can see 2 solutions:
* prevent NPCs to react to other NPCs' chat
* add a static variable somewhere to prevent infinite recursion

First solution I wonder if that wouldn't break maps?

Probably a good compromise is just a static variable in talk_to_npc function.

Opinions?

Nicolas