hw_UnregisterCallback -- unregister a callback (V6.0)
Synopsis
void hw_UnregisterCallback(APTR handle);
Function
This function can be used to unregister a callback registered by hw_RegisterCallback().
It is normally not necessary to call this function since Hollywood unregisters all callbacks
before it exits.
Note that before Hollywood 9.0 this function was badly broken and trashed
internal lists. Do not use with Hollywood versions older than 9.0.