More Bank Additions

Bank is now tracking borrowed money and owed money.
Having a bit of trouble having the bank remember how much was owed.
Probably need to switch the variables to global, or pointers.
Still need to figure out a way to prevent the player from borrowing more
money than the bank has. I currently stop them from borrowing when it's
already at -/0, but haven't figured out a way to prevent them from
taking out more than the bank has. For example, if the bank has 100, you
can pull out 1000. If the bank has -1, you can't pull out anything.