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

i.e. world update start

src/server/game/Weather/Weather.cpp

@@ -12,6 +12,7 @@
 #include "WorldPacket.h"
 #include "Player.h"
 #include "World.h"
+#include "GameTime.h"
 #include "Log.h"
 #include "ObjectMgr.h"
 #include "Util.h"
@@ -82,7 +83,7 @@ bool Weather::ReGenerate()
 
     //78 days between January 1st and March 20nd; 365/4=91 days by season
     // season source http://aa.usno.navy.mil/data/docs/EarthSeasons.html
-    time_t gtime = sWorld->GetGameTime();
+    time_t gtime = GameTime::GetGameTime();
     struct tm ltime;
     ACE_OS::localtime_r(&gtime, &ltime);
     uint32 season = ((ltime.tm_yday - 78 + 365)/91)%4;