The arrow of time

List of changes from Pawel's commit message:

 Update ZFS from version 6 to 13 and bring some FreeBSD-specific changes.

 This bring huge amount of changes, I'll enumerate only user-visible changes:

 - Delegated Administration

       Allows regular users to perform ZFS operations, like file system
       creation, snapshot creation, etc.

 - L2ARC

       Level 2 cache for ZFS - allows to use additional disks for cache.
       Huge performance improvements mostly for random read of mostly
       static content.

 - slog

       Allow to use additional disks for ZFS Intent Log to speed up
       operations like fsync(2).

 - vfs.zfs.super_owner

       Allows regular users to perform privileged operations on files stored
       on ZFS file systems owned by him. Very careful with this one.

 - chflags(2)

       Not all the flags are supported. This still needs work.

 - ZFSBoot

       Support to boot off of ZFS pool. Not finished, AFAIK.

       Submitted by:   dfr

 - Snapshot properties

 - New failure modes

       Before if write requested failed, system paniced. Now one
       can select from one of three failure modes:
       - panic - panic on write error
       - wait - wait for disk to reappear
       - continue - serve read requests if possible, block write requests

 - Refquota, refreservation properties

       Just quota and reservation properties, but don't count space consumed
       by children file systems, clones and snapshots.

 - Sparse volumes

       ZVOLs that don't reserve space in the pool.

 - External attributes

       Compatible with extattr(2).

 - NFSv4-ACLs

       Not sure about the status, might not be complete yet.

       Submitted by:   trasz

 - Creation-time properties

 - Regression tests for zpool(8) command.