HAL Port is using a special handle, where the module and pin are bit
shifted straight into the handle. This is one of the few special cases
we have, but for the way port is used it is much cleaner and uses much
less memory. Plus it is generic and not specific to one type.
Internally, the linked list now uses shared_ptrs instead of raw
pointers. In addition, in the WPILib the notifier handle is now made
atomic. Then before the class is destructed, the handle is now set to 0.
This should help solve one of the existing race conditions. A 0 handle
is correctly handled down at the HAL level.
Handles will be replacing opaque pointers in the HAL for better compatibility and easier error checking. This commits adds the initial resource manangement and definition for handles.
