feat(core): Ensure that all actions are compared to fixed point in time (#1236) (#1458)

i.e. world update start

src/server/game/Time/GameTime.cpp

@@ -0,0 +1,57 @@
+/*
+ * 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/>
+ */
+
+#include "GameTime.h"
+#include "Timer.h"
+
+namespace GameTime
+{
+    time_t const StartTime = time(nullptr);
+
+    time_t GameTime = time(nullptr);
+    uint32 GameMSTime = 0;
+
+    std::chrono::system_clock::time_point GameTimeSystemPoint = std::chrono::system_clock::time_point::min();
+    std::chrono::steady_clock::time_point GameTimeSteadyPoint = std::chrono::steady_clock::time_point::min();
+
+    time_t GetStartTime()
+    {
+        return StartTime;
+    }
+
+    time_t GetGameTime()
+    {
+        return GameTime;
+    }
+
+    uint32 GetGameTimeMS()
+    {
+        return GameMSTime;
+    }
+
+    std::chrono::system_clock::time_point GetGameTimeSystemPoint()
+    {
+        return GameTimeSystemPoint;
+    }
+
+    std::chrono::steady_clock::time_point GetGameTimeSteadyPoint()
+    {
+        return GameTimeSteadyPoint;
+    }
+
+    uint32 GetUptime()
+    {
+        return uint32(GameTime - StartTime);
+    }
+
+    void UpdateGameTimers()
+    {
+        GameTime = time(nullptr);
+        GameMSTime = getMSTime();
+        GameTimeSystemPoint = std::chrono::system_clock::now();
+        GameTimeSteadyPoint = std::chrono::steady_clock::now();
+    }
+}