Added the interface implementation structures.
I remembered from an email that even when asked for a
IDirectInputDeviceA what was returned was an IDirectInputDevice2A so I
considered that we would only implement the latter. The
IDirectInputDeviceA_xxx methods have been renamed to
IDirectInputDevice2A_xxx, and we always return our IDirectInputDevice2A
implementation as before.
Renamed the implementation structures to XxxImpl.