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

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

Dtrace: Add SUN MDB-like type-aware print() action.

Merge change from illumos:

1694 Add type-aware print() action

This is a very nice feature implemented in upstream Dtrace.
A complete description is available here:
http://dtrace.org/blogs/eschrock/2011/10/26/your-mdb-fell-into-my-dtrace/

This change bumps the DT_VERS_* number to 1.9.0 in
accordance to what is done in illumos.

While here also include some minor cleanups to ease further merging
and appease clang with a fix by Fabian Keil.

Illumos Revisions: 13501:c3a7090dbc16
13483:f413e6c5d297

Reference:
https://www.illumos.org/issues/1560
https://www.illumos.org/issues/1694

Tested by: Fabian Keil
Obtained from: Illumos
MFC after: 1 month

Tag vendor/illumos/dist as 20120614 (illumos-gate 13742:b6bbdd77139c)

Update vendor/illumos/dist to pre libzfs_core state (dtrace and ctf part)
illumos-gate revision 13742:b6bbdd77139c

Obtained from: ssh://anonhg@hg.illumos.org/illumos-gate