Various fixins...

- Fix @run command to lower-case section and filename, and add .ref
- Set battle flag when @busy is called
- Redraw map after exiting the buy/sell manager
- Fix Sell confirmation
- Check the CON file every time mail is checked automatically
- Turn off the battle flag when returning from a hotspot module
- Fix box with calculation in draw_box
- Fix sell manager first draw colour after unsellable item
- Clear message area when an item is used
- Run the busy routing in gametxt.ref when battle is set
- Actually allow doing things with items