4374 dn_free_ranges should use range_tree_t
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Max Grossman <max.grossman@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com
Reviewed by: Garrett D'Amore <garrett@damore.org>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Approved by: Dan McDonald <danmcd@omniti.com>
4752 fan out read zio taskqs
Reviewed by: George Wilson <george.wilson@delphix.com>
Reviewed by: Matthew Ahrens <mahrens@delphix.com>
Reviewed by: Christopher Siden <christopher.siden@delphix.com>
Reviewed by: Eric Schrock <eric.schrock@delphix.com>
Reviewed by: Dan McDonald <danmcd@omniti.com>
Approved by: Dan McDonald <danmcd@omniti.com>
	[illumos-gate merge]

commit 1b497ab83e8f1c58bba5da59c649207a442a4720
    4752 fan out read zio taskqs
commit bf16b11e8deb633dd6c4296d46e92399d1582df4
    4374 dn_free_ranges should use range_tree_t

Conflicts:
	usr/src/uts/common/fs/zfs/vdev_disk.c (copyright)
	usr/src/lib/libzpool/common/sys/zfs_context.h (copyright)