no pneumatic relay sound on brake acting speed change, enabled playback of multiple bookend sounds, extra pantograph control for ai during longer stops, shadow angle calculation tweak, moon appearance tweak, minor bug fixes

simulation.cpp

@@ -820,6 +820,11 @@ state_manager::deserialize_dynamic( cParser &Input, scene::scratch_data &Scratch
         }
     }
     else {
+        if( vehicle->MyTrack != nullptr ) {
+            // rare failure case where vehicle with length of 0 is added to the track,
+            // treated as error code and consequently deleted, but still remains on the track
+            vehicle->MyTrack->RemoveDynamicObject( vehicle );
+        }
         delete vehicle;
         skip_until( Input, "enddynamic" );
         return nullptr;