function determines whether the ACL pointed to by the argument
Upon successful completion, the location referred to by the argument
will be set to 1, if the ACL
points to is trivial, or 0 if it's not.
ACL is trivial if it can be fully expressed as a file mode without losing
any access rules.
For POSIX.1e ACLs, ACL is trivial if it has the three required entries,
one for owner, one for owning group, and one for other.
For NFSv4 ACLs, ACL is trivial if it is identical to the ACL generated by
Files that have non-trivial ACL have a plus sign appended after mode bits
in "ls -l" output.