refactor(Core/Tools): remove ACE from tools (#3351)

src/common/Threading/PolicyLock.h

@@ -0,0 +1,16 @@
+/*
+* Copyright (C) 2016+     AzerothCore <www.azerothcore.org>, released under GNU GPL v2 license: https://github.com/azerothcore/azerothcore-wotlk/blob/master/LICENSE-GPL2
+* Copyright (C) 2008-2016 TrinityCore <http://www.trinitycore.org/>
+* Copyright (C) 2005-2009 MaNGOS <http://getmangos.com/>
+*/
+
+#ifndef POLICYLOCK_H
+#define POLICYLOCK_H
+
+#include <mutex>
+
+#define RETURN_GUARD(mutex, retval) if (!mutex.try_lock())    \
+                                        return retval;        \
+                                    std::lock_guard<decltype(mutex)> guard(mutex, std::adopt_lock)
+
+#endif