World|Sector: Improved sector cluster linking wrt independent but nes…

…ted hacks

This iteration of the linking algorithm resolves cases such as the
twin balcony bridge in requiem.wad MAP13 and the nukeage pools in
av.wad MAP01 (the latter is not yet completely fixed, however).

doomsday/client/src/world/sector.cpp

@@ -73,11 +73,10 @@ void Sector::Cluster::remapVisPlanes()
                         if(otherLeaf.hasCluster())
                         {
                             Cluster *otherCluster = &otherLeaf.cluster();
-                            if(otherCluster != this)
+                            if(otherCluster != this &&
+                               otherCluster->_mappedVisFloor != this &&
+                               !(!_allSelfRefBoundary && otherCluster->_allSelfRefBoundary))
                             {
-                                if(!_allSelfRefBoundary && otherCluster->_allSelfRefBoundary)
-                                    return;
-
                                 // Remember the exterior cluster.
                                 exteriorCluster = otherCluster;
                             }
@@ -106,9 +105,11 @@ void Sector::Cluster::remapVisPlanes()
             }
             else
             {
-                // Reverse the linkage (this cluster is containted).
+                // This cluster is containted. Remove linkage from exterior to
+                // this thereby forcing it to be re-evaluated (however next time
+                // a different cluster will be selected from the boundary).
                 exteriorCluster->_mappedVisFloor =
-                    exteriorCluster->_mappedVisCeiling = exteriorCluster;
+                    exteriorCluster->_mappedVisCeiling = 0;
             }
         }