Window layout

- Tidies up the default window layout (see https://github.com/bensemmler/angband/wiki/OS-X-Window-Layout).
- Tries to respect the user's window visibility settings regardless of the subwindow flags. This way, users won't have to close unwanted windows each time they launch the game. It also allows terms 6 and 7 to be hidden on a new game (even though the subwindow flags are set). The only drawback is that if a user turns on a subwindow flag that was previously off, the window will not immediately open as it has in the past. Also, switching between saves with different subwindow flag settings may have a similar effect. The window just needs to be opened from the Window menu and visibility will be restored.