Monster ranged attacks and staying away from hero

Move the check for monsters that want to stay away from hero
due to having a ranged attack into a separate function.

Add monsters with polearms and breath attacks to it.
Monsters with breath attacks stay away only if they haven't
used their breath recently, or if they are injured.

include/hack.h

@@ -475,6 +475,9 @@ enum bodypart_types {
 #define TELEDS_ALLOW_DRAG 1
 #define TELEDS_TELEPORT   2
 
+#define MON_POLE_DIST 5 /* How far monsters can use pole-weapons */
+#define PET_MISSILE_RANGE2 36 /* Square of distance within which pets shoot */
+
 /*
  * option setting restrictions
  */