- link actors into blockmap through linked line portals.

Links through sector portals are not done because nearly all the checks can be performed without doing this so if it works without there's no need to add more processing time.
Will have to see if there's cases left where such a link is needed and if so, whether there's better options to do it.

For line portals such links are necessary to have proper collision detection with actors that are currently transitioning the portal.

src/portal.cpp

@@ -1107,7 +1107,25 @@ void P_CreateLinkedPortals()
 			}
 		}
 	}
-	//BuildBlockmap();
+	if (linkedPortals.Size() > 0)
+	{
+		// We need to relink all actors that may touch a linked line portal
+		TThinkerIterator<AActor> it;
+		AActor *actor;
+		while ((actor = it.Next()))
+		{
+			if (!(actor->flags & MF_NOBLOCKMAP))
+			{
+				FPortalGroupArray check(FPortalGroupArray::PGA_NoSectorPortals);
+				P_CollectConnectedGroups(actor->Sector->PortalGroup, actor->Pos(), actor->Top(), actor->radius, check);
+				if (check.Size() > 0)
+				{
+					actor->UnlinkFromWorld();
+					actor->LinkToWorld();
+				}
+			}
+		}
+	}
 }
 
 
@@ -1208,7 +1226,7 @@ bool P_CollectConnectedGroups(int startgroup, const fixedvec3 &position, fixed_t
 			wsec = P_PointInSector(dx, dy);	// get lower sector at the exact spot we want to check and repeat
 			retval = true;
 		}
-		if (out.method == FPortalGroupArray::PGA_Full3d)
+		if (out.method == FPortalGroupArray::PGA_Full3d && PortalBlockmap.hasLinkedSectorPortals)
 		{
 			groupsToCheck.Clear();
 			groupsToCheck.Push(startgroup);