- Copy stable/10 (r259064) to releng/10.0 as part of the
10.0-RELEASE cycle.
- Update __FreeBSD_version [1]
- Set branch name to -RC1

[1] 10.0-CURRENT __FreeBSD_version value ended at '55', so
start releng/10.0 at '100' so the branch is started with
a value ending in zero.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

Merge recent zfs vendor changes, sync code and adjust userland DEBUG.

Illumos issued covered:
1884 Empty "used" field for zfs *space commands
3006 VERIFY[S,U,P] and ASSERT[S,U,P] frequently check if first argument
is zero
3028 zfs {group,user}space -n prints (null) instead of numeric GID/UID
3048 zfs {user,group}space [-s|-S] is broken
3049 zfs {user,group}space -t doesn't really filter the results
3060 zfs {user,group}space -H output isn't tab-delimited
3061 zfs {user,group}space -o doesn't use specified fields order
3064 usr/src/cmd/zpool/zpool_main.c misspells "successful"
3093 zfs {user,group}space's -i is noop
3098 zfs userspace/groupspace fail without saying why when run as non-root

References:
https://www.illumos.org/issues/ + [issue_id]

Obtained from: illumos (vendor/illumos, vendor/illumos-sys)
MFC after: 2 weeks

Finally... Import the latest open-source ZFS version - (SPA) 28.

Few new things available from now on:

- Data deduplication.
- Triple parity RAIDZ (RAIDZ3).
- zfs diff.
- zpool split.
- Snapshot holds.
- zpool import -F. Allows to rewind corrupted pool to earlier
transaction group.
- Possibility to import pool in read-only mode.

MFC after: 1 month

Forced commit to note that these files were repo copied.

Please welcome ZFS - The last word in file systems.

ZFS file system was ported from OpenSolaris operating system. The code in under
CDDL license.

I'd like to thank all SUN developers that created this great piece of software.

Supported by: Wheel LTD (http://www.wheel.pl/)
Supported by: The FreeBSD Foundation (http://www.freebsdfoundation.org/)
Supported by: Sentex (http://www.sentex.net/)