Refactor Creature::SelectNearestTarget(float dist)

This function is used in many scripts to find the nearest enemy within the given distance.
However, it had an implicit limit to the ATTACK_DISTANCE. so in many case the "dist" was in fact just ignored.
In other case, the ATTACK_DISTANCE is required. So 2 functions are necessary to avoid ambiguities.

The refactoring is the split of the function in 2: SelectNearestTarget and SelectNearestTargetInAttackDistance.

--HG--
branch : trunk

src/game/UnitAI.cpp

@@ -323,5 +323,5 @@ void SimpleCharmedAI::UpdateAI(const uint32 /*diff*/)
 
     Unit *target = me->getVictim();
     if (!target || !charmer->canAttack(target))
-        AttackStart(charmer->SelectNearestTarget());
+        AttackStart(charmer->SelectNearestTargetInAttackDistance());
 }