Add Check for Understanding on A0_result_parameters

[robertdfrench]

This is where we go over the data structures and conventions used for packing / unpacking arguments to / from door_calls, but there are no "Check for Understanding" questions at the bottom. It's a critical point for anyone wanting to work with the Doors API, so it's worth providing folks a way to convince themselves that they know what's going on. AND! Some of these structures are kindof subtle if you don't spend the majority of your time in C.