- changed handling of one-time, one-way door polyobjects to be more efficient.

The old code kept the dead thinker, resulting in constant deletion and recreation of the subsector links and PolyBSP because the interpolation kept running.
Changed it so that the thinker is destroyed and the polyobject gets blocked by setting a new flag.

src/p_saveg.cpp

@@ -540,6 +540,14 @@ void P_SerializePolyobjs (FArchive &arc)
 		for(i = 0, po = polyobjs; i < po_NumPolyobjs; i++, po++)
 		{
 			arc << po->tag << po->Angle << po->StartSpot.pos << po->interpolation;
+			if (SaveVersion >= 4537)
+			{
+				arc << po->bBlocked;
+			}
+			else
+			{
+				po->bBlocked = false;
+			}
   		}
 	}
 	else