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)