Move internal windows when main window is resized

[Ters]

When moving a maximized Simutrans from a bigger monitor to a smaller monitor, a vehicle information window at the old right edge of the main window was now suddenly beyond the new right edge. At the moment, I noticed something seemed to have gone missing, but didn't quite realize what and didn't bother checking. Shortly after, I was very puzzled that I was unable to query a certain vehicle. All I got was all the other information windows for things on the same tile. I eventually realized that it was that vehicle's information window that had been to the far right before, and was still open out of sight. A tap on backspace and I was able to bring up the vehicle's information window with the visible region. This is something that may really confuse players.