- made setting actor TID more explicit

Now it's no longer possible to manipulate TID hash from arbitrary location
For example, this prevents linking of destroyed object into the hash
TID member is still public but writing to it is limited to a few very specific cases like serialization and player traveling between levels

https://forum.zdoom.org/viewtopic.php?t=64476

src/d_net.cpp

@@ -2400,12 +2400,11 @@ void Net_DoCommand (int type, uint8_t **stream, int player)
 							if (type >= DEM_SUMMON2 && type <= DEM_SUMMONFOE2)
 							{
 								spawned->Angles.Yaw = source->Angles.Yaw - angle;
-								spawned->tid = tid;
 								spawned->special = special;
 								for(i = 0; i < 5; i++) {
 									spawned->args[i] = args[i];
 								}
-								if(tid) spawned->AddToHash();
+								if(tid) spawned->SetTID(tid);
 							}
 						}
 					}