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/CreatureAI.h

@@ -73,8 +73,6 @@ class CreatureAI : public UnitAI
         bool UpdateVictimWithGaze();
         bool UpdateCombatState();
 
-        void SelectNearestTarget(Unit *who);
-
         void SetGazeOn(Unit *target);
 
         Creature *DoSummon(uint32 uiEntry, const Position &pos, uint32 uiDespawntime = 30000, TempSummonType uiType = TEMPSUMMON_CORPSE_TIMED_DESPAWN);