Dynamic Creature/Go spawning:

- True blizzlike creature spawn/respawn behavior - new creature = new object
 - Toggleable spawn groups (with C++/SAI/command options to use them)
 - Custom feature: dynamic spawn rate scaling. Accelerates respawn rate based on players in the zone.
 - Backward compatibility mode (set via group and for summons)
   to support creatures/gos that currently don't work well with this
   (this should be removed once the exceptions are fixed)

Fixes and closes #2858
Tags #8661 as fixable.
Fixes and closes #13787
Fixes #15222.

src/server/scripts/Commands/cs_misc.cpp

@@ -1911,10 +1911,22 @@ public:
             return true;
         }
 
+        // First handle any creatures that still have a corpse around
         Trinity::RespawnDo u_do;
         Trinity::WorldObjectWorker<Trinity::RespawnDo> worker(player, u_do);
         Cell::VisitGridObjects(player, worker, player->GetGridActivationRange());
 
+        // Now handle any that had despawned, but had respawn time logged.
+        RespawnVector data;
+        player->GetMap()->GetRespawnInfo(data, SPAWN_TYPEMASK_ALL, 0);
+        if (!data.empty())
+        {
+            uint32 const gridId = Trinity::ComputeGridCoord(player->GetPositionX(), player->GetPositionY()).GetId();
+            for (RespawnInfo* info : data)
+                if (info->gridId == gridId)
+                    player->GetMap()->RemoveRespawnTime(info, true);
+        }
+
         return true;
     }