Export additional dsl symbols

Principly these symbols were exported to get access to the
dsl_prop_register/dsl_prop_unregister functions.  They allow
us to cleanly register a callback which is called when a
dataset property is modified.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Document the zle compression algorithm

Signed-off-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Improve error message consistency

Signed-off-by: Richard Laager <rlaager@wiktel.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Illumos #1680: zfs vdev_file_io_start: validate vdev before using vdev_tsd

vdev_tsd can be NULL for certain vdev states.
At least in userland testing with ztest.

References to Illumos issue:
  https://www.illumos.org/issues/1680

Ported-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #655
OS-926: zfs panic in zfs_fill_zplprops_impl()

This change appears to be exclusive to SmartOS. It is not present in
illumos-gate but it just adds some needed error handling.  This is
clearly preferable to simply ASSERTING which is what would occur
prior to the patch.

Reviewed by: Jerry Jelinek <jerry.jelinek@joyent.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Ported-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #652
Illumos #1951: leaking a vdev when removing an l2cache device

1952 memory leak when adding a file-based l2arc device
1954 leak in ZFS from metaslab_group_create and zfs_ereport_checksum

Reviewed by: Adam Leventhal <ahl@delphix.com>
Reviewed by: Matt Ahrens <matt@delphix.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Bill Pijewski <wdp@joyent.com>
Reviewed by: Dan McDonald <danmcd@nexenta.com>
Approved by: Eric Schrock <eric.schrock@delphix.com>

References to Illumos issues:
  https://www.illumos.org/issues/1951
  https://www.illumos.org/issues/1952
  https://www.illumos.org/issues/1954

Ported-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #650
Illumos #1475: zfs spill block hold can access invalid spill blkptr

Reviewed by: Dan McDonald <danmcd@nexenta.com>
Reviewed by: Gordon Ross <gwr@nexenta.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: George Wilson <gwilson@zfsmail.com>
Approved by: Garrett D'Amore <garrett@nexenta.com>

References to Illumos issue:
  https://www.illumos.org/issues/1475

Ported-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #648
Illumos #1346: zfs incremental receive may leave behind temporary clones

1356 zfs dataset prefetch code not working
Reviewed by: Matthew Ahrens <matt@delphix.com>
Reviewed by: Dan McDonald <danmcd@nexenta.com>
Approved by: Gordon Ross <gwr@nexenta.com>

References to Illumos issue:
  https://www.illumos.org/issues/1346
  https://www.illumos.org/issues/1356

Ported-by: Richard Yao <ryao@cs.stonybrook.edu>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #647
ZFS snapshot alias

For consistency, and because it's handy, add the 'zfs snap' alias which
was introduced by Oracle Solaris 11.  This includes an update to the
man page to reflect all the available alias (snap, umount, and recv).

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #640
ZFS list snapshot property alias

Add support for the `zfs list -t snap` alias which is available under
Oracle Solaris 11.

Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #640