they label, derive that information implicitly from the set of label
initializers in their policy operations set. This avoids a possible
class of programmer errors, while retaining the structure that
allows us to avoid allocating labels for objects that don't need
them. As before, we regenerate a global mask of labeled objects
each time a policy is loaded or unloaded, stored in mac_labeled.
Discussed with: csjp
Suggested by: Jacques Vidrine <nectar at apple.com>
Obtained from: TrustedBSD Project
Sponsored by: Apple, Inc.