Core/SmartScripts: added new action SMART_ACTION_COMBAT_STOP

* this avoid using hacks like evade, faction change or rooting. I wonder how SAI could be without this

(cherry picked from commit d68df33c7689d62e27787f75820fd5b5be94005f)

src/server/game/AI/SmartScripts/SmartScript.cpp

@@ -765,6 +765,15 @@ void SmartScript::ProcessAction(SmartScriptHolder& e, Unit* unit, uint32 var0, u
                         player->GroupEventHappens(e.action.quest.quest, GetBaseObject());
             break;
         }
+        case SMART_ACTION_COMBAT_STOP:
+        {
+            if (!me)
+                break;
+
+            me->CombatStop(true);
+            TC_LOG_DEBUG("scripts.ai", "SmartScript::ProcessAction:: SMART_ACTION_COMBAT_STOP: %s CombatStop", me->GetGUID().ToString().c_str());
+            break;
+        }
         case SMART_ACTION_REMOVEAURASFROMSPELL:
         {
             ObjectList* targets = GetTargets(e, unit);