Migrate ZFS-* message descriptions (#49)

Prerequisite for changing the URLs in the command outputs from
zfsonlinux.org to openzfs.github.io/openzfs-docs/

Signed-off-by: Ryan Moeller <ryan@iXsystems.com>

docs/msg/ZFS-8000-A5/index.rst

@@ -0,0 +1,83 @@
+..
+   CDDL HEADER START
+
+   The contents of this file are subject to the terms of the
+   Common Development and Distribution License (the "License").
+   You may not use this file except in compliance with the License.
+
+   You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
+   or http://www.opensolaris.org/os/licensing.
+   See the License for the specific language governing permissions
+   and limitations under the License.
+
+   When distributing Covered Code, include this CDDL HEADER in each
+   file and include the License file at usr/src/OPENSOLARIS.LICENSE.
+   If applicable, add the following below this CDDL HEADER, with the
+   fields enclosed by brackets "[]" replaced with your own identifying
+   information: Portions Copyright [yyyy] [name of copyright owner]
+
+   CDDL HEADER END
+
+   Portions Copyright 2007 Sun Microsystems, Inc.
+
+.. highlight:: none
+
+Message ID: ZFS-8000-A5
+=======================
+
+Incompatible version
+--------------------
+
++-------------------------+------------------------------------------------+
+| **Type:**               | Error                                          |
++-------------------------+------------------------------------------------+
+| **Severity:**           | Major                                          |
++-------------------------+------------------------------------------------+
+| **Description:**        | The on-disk version is not compatible with the |
+|                         | running system.                                |
++-------------------------+------------------------------------------------+
+| **Automated Response:** | No automated response will occur.              |
++-------------------------+------------------------------------------------+
+| **Impact:**             | The pool is unavailable.                       |
++-------------------------+------------------------------------------------+
+
+.. rubric:: Suggested Action for System Administrator
+
+If this error is seen during ``zpool import``, see the section below.
+Otherwise, run ``zpool status -x`` to determine which pool is faulted:
+
+::
+
+   # zpool status -x
+     pool: test
+    state: FAULTED
+   status: The ZFS version for the pool is incompatible with the software running
+           on this system.
+   action: Destroy and re-create the pool.
+    scrub: none requested
+   config:
+
+           NAME                  STATE     READ WRITE CKSUM
+           test                  FAULTED      0     0     0  incompatible version
+             mirror              ONLINE       0     0     0
+               sda9              ONLINE       0     0     0
+               sdb9              ONLINE       0     0     0
+
+   errors: No known errors
+
+The pool cannot be used on this system.  Either move the storage to
+the system where the pool was originally created, upgrade the current
+system software to a more recent version, or destroy the pool and
+re-create it from backup.
+
+If this error is seen during import, the pool cannot be imported on
+the current system.  The disks must be attached to the system which
+originally created the pool, and imported there.
+
+The list of currently supported versions can be displayed using
+``zpool upgrade -v``.
+
+.. rubric:: Details
+
+The Message ID: ``ZFS-8000-A5`` indicates a version mismatch exists
+between the running system and the on-disk data.