Client-side support for NFSv4 ACLs.  Exports the raw xdr code via the
 system.nfs4_acl extended attribute.  It is up to userspace to decode the acl
 (and to provide correctly xdr'd acls on setxattr), and to convert to/from
 POSIX ACLs if desired.

 This patch provides only the read support.
Signed-off-by: NJ. Bruce Fields <bfields@citi.umich.edu>
Signed-off-by: NTrond Myklebust <Trond.Myklebust@netapp.com>