Underground data is not saved

[Hanse00]

I don't know weather this is intentional or a bug, but it seems like the underground view does not save map data.

This is rather annoying if you live in an underground base, or similar, where you'd like the minimap to save the layout of the place.

[Lunatrius]

Switching dimensions will sometimes cause the underground maps of different dimensions to overlap over each other. Don't happen always, but it's often enough to be noticeable.