This function determines the visibility of objects in the
kernel based on the group IDs in the credentials
associated with them.
The visibility of objects is influenced by the
If this variable is non-zero then all objects in the kernel
are visible to each other irrespective of their group membership.
If this variable is zero then the object with credentials
is visible to the object with credentials
is the super-user credential, or if at least one of
u1, Ns, 's
group IDs is present in
u2, Ns, 's