Check and refactor new reverse-box-collision code

[GoogleFrog]

Test the reverse box collision code. It appears to work.

The code is due to be refactored as the current implementation uses a boolean array and an array of boxes when the functions should now be passed a list of reverse boxes and a list of forwards boxes. Perhaps splitting up the list is unreasonable, the list could instead have list.iterator.nextReverse and list.iterator.nextForwards if that is a reasonable thing. In any case the structure of the current code is made fragile due to the naked boolean array.