Add ZFS support to the bsdinstall partition editor and sade.

Submitted by:	Kurt Lidl (original version)
MFC after:	6 weeks
We don't need an exclusive object lock on the expected execution path
through {ext2,ffs}_getpages().

Reviewed by:	kib, pfg
MFC after:	6 weeks
Sponsored by:	EMC / Isilon Storage Division
Add the new iscsi(4) man page
Cross reference it from iscsid(8) and iscsictl(8)

Reviewed by:	trasz
Approved by:	bcr (mentor), wblock (mentor)
Sponsored by:	ScaleEngine Inc.
CR:		https://reviews.freebsd.org/D741
Switch if_vlan(4) to rmlock.

MFC after:	2 weeks