acl(9): expound on NFSv4 constants' meanings

This change adds missing documentation for various NFSv4 constants
supported by acl(9).

Bump `.Dd` for the change.

MFC after:	1 week
Reviewed by:	rmacklem
Differential Revision:	https://reviews.freebsd.org/D58736

share/man/man9/acl.9

@@ -23,7 +23,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd September 4, 2015
+.Dd October 10, 2026
 .Dt ACL 9
 .Os
 .Sh NAME
@@ -165,6 +165,7 @@ The process may write to the associated file.
 Same as
 .Dv ACL_WRITE_DATA .
 .It Dv ACL_APPEND_DATA
+The process may append to the associated file.
 .It Dv ACL_ADD_SUBDIRECTORY
 Same as
 .Dv ACL_APPEND_DATA .
@@ -175,12 +176,21 @@ Ignored.
 .It Dv ACL_EXECUTE
 The process may execute the associated file.
 .It Dv ACL_DELETE_CHILD
+The process may delete a file or directory within a directory.
 .It Dv ACL_READ_ATTRIBUTES
+The process may read basic attributes (non-ACLs) of a file or directory.
 .It Dv ACL_WRITE_ATTRIBUTES
+The process may change the times, mimetype, hidden, and system attributes
+associated with a file or directory,
 .It Dv ACL_DELETE
+The process may delete a file or directory.
 .It Dv ACL_READ_ACL
+The process may read the ACL or mode attributes for a file or directory.
 .It Dv ACL_WRITE_ACL
+The process may write the ACL or mode attributes for a file or directory.
 .It Dv ACL_WRITE_OWNER
+The process may write the owner and owner_group attributes for a file or
+directory.
 .It Dv ACL_SYNCHRONIZE
 Ignored.
 .El
@@ -218,6 +228,13 @@ and directories.
 .Xr VOP_ACLCHECK 9 ,
 .Xr VOP_GETACL 9 ,
 .Xr VOP_SETACL 9
+.Sh STANDARDS
+.Rs
+.%U https://www.ietf.org/ietf-ftp/rfc/rfc8881.pdf
+.%T Network File System (NFS) Version 4 Minor Version 1 Protocol
+.%R RFC 8881
+.%D August 2020
+.Re
 .Sh AUTHORS
 This manual page was written by
 .An Robert Watson .