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/GridNotifiers.h

@@ -940,6 +940,31 @@ namespace Trinity
 
     // Creature checks
 
+    class NearestHostileUnitCheck
+    {
+        public:
+            explicit NearestHostileUnitCheck(Creature const* creature, float dist = 0) : me(creature)
+            {
+                m_range = (dist == 0 ? 9999 : dist);
+            }
+            bool operator()(Unit* u)
+            {
+                if (!me->IsWithinDistInMap(u, m_range))
+                    return false;
+
+                if (!me->canAttack(u))
+                    return false;
+
+                m_range = me->GetDistance(u);   // use found unit range as new range limit for next check
+                return true;
+            }
+
+    private:
+            Creature const *me;
+            float m_range;
+            NearestHostileUnitCheck(NearestHostileUnitCheck const&);
+    };
+
     class NearestHostileUnitInAttackDistanceCheck
     {
         public:
@@ -950,7 +975,6 @@ namespace Trinity
             }
             bool operator()(Unit* u)
             {
-                // TODO: addthreat for every enemy in range?
                 if (!me->IsWithinDistInMap(u, m_range))
                     return false;
 
@@ -965,7 +989,7 @@ namespace Trinity
                         return false;
                 }
 
-                m_range = me->GetDistance(u);
+                m_range = me->GetDistance(u);   // use found unit range as new range limit for next check
                 return true;
             }
             float GetLastRange() const { return m_range; }