UpdateSystemActivity() is defined in OSServices/Power.h which is
erroneously #ifndef _LP64 in the 10.5 SDK. Since OSServices is a
sub-framework of the CoreServices, Power.h cannot be included
directly without specifying the long and messy path to it.
Just declare it extern here as well instead.
Don’t disable dynamic updating of the bluetooth device name as it
would then be printed as (null) on the first pairing of a wiimote.