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

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

MFV r247844 (illumos-gate 13975:ef6409bc370f)

Illumos ZFS issues:
3582 zfs_delay() should support a variable resolution
3584 DTrace sdt probes for ZFS txg states

Provide a compatibility shim for Solaris's cv_timedwait_hires
to help aid future porting.

Approved by: re (ZFS blanket)

Remove the extra parenthesis from the cv_init() macro. They are not
necessary because we already use parenthesis in zfs_cv_init().

This fixes a long standing bug where there would be an extra ")" at the
end of the string. This extra parenthesis would show up in the WCHAN of
the process (top, stty status, etc.).

Forced commit to note that these files were repo copied.

Remove "zfs:" prefix from lock and condvar names and also skip non-letter
characters (mostly "&"). Because top(1) shows only first six characters of
wait channel, without this change we saw only one meaningful character.

Requested by: kris & others
MFC after: 1 week

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/)