MFC r326276:

various: general adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

No functional change intended.

Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

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

Move the old iSCSI initiator source to a more appropriate place
(sys/dev/iscsi_initiator/ instead of sys/dev/iscsi/initiator/), to make
room for the new one. This is also more logical location (kernel module
being named iscsi_initiator.ko, for example). There is no ongoing work
on this I know of, so it shouldn't make life harder for anyone.

There are no functional changes, apart from "svn mv" and adjusting paths.

Remove includes for old versions of FreeBSD.

Reviewed by: stass
Obtained From: DragonFlyBSD
MFC After: 1 week

- Add full support for header / data digests.
- Increase target limit from 4 to 64; this limit will be removed entirely
at a later time.
- Improve recovery from lost network connections.
- Fix some potential deadlocks and a serious memory leak.
- Fix incorrect use of MH_ALIGN (instead of M_ALIGN), which makes no
practical difference, but triggers a KASSERT with INVARIANTS.
- Fix some warnings in iscontrol(8) and improve the man page somewhat.

Submitted by: Daniel Braniss <danny@cs.huji.ac.il>
Sponsored by: Dansk Scanning A/S, Data Robotics Inc.

Big update to the iSCSI initiator code. Highlights include IPv6 support,
many bugs fixes, many more performance improvements.

Submitted by: Danny Braniss

M sbin/iscontrol/iscsi.conf.5
M sbin/iscontrol/iscontrol.8
M sbin/iscontrol/iscontrol.h
M sbin/iscontrol/config.c
M sbin/iscontrol/fsm.c
M sbin/iscontrol/login.c
M sbin/iscontrol/pdu.c
M sbin/iscontrol/misc.c
M sbin/iscontrol/auth_subr.c
M sbin/iscontrol/iscontrol.c
M sys/dev/iscsi/initiator/isc_cam.c
M sys/dev/iscsi/initiator/iscsi.h
M sys/dev/iscsi/initiator/isc_soc.c
M sys/dev/iscsi/initiator/iscsi_subr.c
M sys/dev/iscsi/initiator/iscsivar.h
M sys/dev/iscsi/initiator/isc_subr.c
M sys/dev/iscsi/initiator/iscsi.c
M sys/dev/iscsi/initiator/isc_sm.c

Introduce Danny Braniss' iSCSI initiator, version 2.0.99. Please read the
included man pages on how to use it. This code is still somewhat experimental
but has been successfully tested on a number of targets. Many thanks to
Danny for contributing this.

Approved by: re