vt(4): Save/restore keyboard mode & LED states when switching window

(MFC of r272416)

Add new functions to manipulate these mode & state, instead of calling
kbdd_ioctl() everyhere.

This fixes at least two bugs:

    1. The state of the Scroll Lock LED and the state of scroll mode
       could be out-of-sync. For instance, if one enables scroll mode on
       window #1 and switches to window #2, the LED would remain on, but
       the window wouldn't be in scroll mode.

       Similarily, when switching between a console and an X.Org
       session, the LED states could be inconsistent with the real
       state.

    2. When exiting from an X.Org session, the user could be unable to
       type anything. The workaround was to switch to another console
       window and come back.

Differential Revision:	https://reviews.freebsd.org/D821
Reviewed by:	ray@
Approved by:	ray@
Tested by:	kwm@
vt(4): Don't recalculate buffer size if we don't know screen size

(MFC of r272537)

When the screen size is unknown, it's set to 0x0. We can't use that as
the buffer size, otherwise, functions such as vtbuf_fill() will fail.

This fixes a panic on RaspberryPi, where there's no vt(4) backend
configured early in boot.

PR:		193981
Tested by:	danilo@
MFH (r272173): offer to enable local_unbound after installation
MFH (r272830): change the hardcoded default back to DES
MFH (r272833): remove last vestige of MD5 password hashes
MFC r272907:
Make MAP_NOSYNC handling in the vm_fault() read-locked object path
compatible with write-locked path.
Fix a missed merge introduced in r272883.
MFC r272502: MFV r272493:

Show individual disk capacity when doing zpool list -v.

Illumos issue:
    5147 zpool list -v should show individual disk capacity
MFC r272932:

Mark iscontrol(8) and iscsi_initiator(4) obsolete.

Differential Revision:	https://reviews.freebsd.org/D931
Reviewed by:	wblock@
Sponsored by:	The FreeBSD Foundation
MFC r271588:  Update CAM CCB accounting for the new status quo.

devq_openings counter lost its meaning after allocation queues has gone.
held counter is still meaningful, but problematic to update due to separate
locking of CCB allocation and queuing.

To fix that replace devq_openings counter with allocated counter.  held is
now calculated on request as difference between number of allocated, queued
and active CCBs.
MFC r272414:
  Merge the following revisions from ^/projects/release-vmimage:

  r272234, r272236, r272262, r272264, r272269, r272271, r272272,
  r272277, r272279, r272376, r272380, r272381, r272392, r272234,
  r272412:

  r272234:
    Initial commit to include virtual machine images as part
    of the FreeBSD release builds.

    This adds a make(1) environment variable requirement,
    WITH_VMIMAGES, which triggers the virtual machine image
    targets when not defined to an empty value.

    Relevant user-driven variables include:

     o VMFORMATS:	The virtual machine image formats to create.
       Valid formats are provided by running 'mkimg --formats'

     o VMSIZE:	The size of the resulting virtual machine
       image.  Typical compression is roughly 140Mb, regardless
       of the target size (10GB, 15GB, 20GB, 40GB sizes have been
       tested with the same result).

     o VMBASE:	The prefix of the virtual machine disk images.
       The VMBASE make(1) environment variable is suffixed with
       each format in VMFORMATS for each individual disk image, as
       well as '.img' for the source UFS filesystem passed to
       mkimg(1).

    This also includes a new script, mk-vmimage.sh, based on how
    the VM images for 10.0-RELEASE, 9.3-RELEASE, and 10.1-RELEASE
    were created (mk-vmimage.sh in ^/user/gjb/thermite/).

    With the order in which the stages need to occur, as well as
    sanity-checking error cases, it makes much more sense to
    execute a shell script called from make(1), using env(1) to
    set specific parameters for the target image than it does to
    do this in make(1) directly.

  r272236:
    Use VMBASE in place of a hard-coded filename in the CLEANFILES
    list.

  r272262:
    Remove a 'set -x' that snuck in during testing.

  r272264:
    release/Makefile:
      Connect the virtual machine image build to the release
      target if WITH_VMIMAGES is set to a non-empty value.

    release/release.sh:
      Add WITH_VMIMAGES to RELEASE_RMAKEFLAGS.

    release/release.conf.sample:
      Add commented entries for tuning the release build if the
      WITH_VMIMAGES make(1) environment variable is set to
      a non-empty value.

  r272269:
    release/Makefile:
      Include .OBJDIR in DESTDIR in the vm-base target.

    release/release.sh:
      Provide the full path to mddev.

  r272271:
    Fix UFS label for the root filesystem.

  r272272:
    Remove comments left in accidentally while testing, so the
    VM /etc/fstab is actually created.

  r272277:
    Remove the UFS label from the root filesystem since it is added
    by mkimg(1) as a gpt label, consistent with the fstab(5) entry.

  r272279:
    Comment cleanup in panic() message when mkimg(1) does not support
    the requested disk image format.

  r272376:
    Separate release/scripts/mk-vmimage.sh to machine-specific
    scripts, making it possible to mimic the functionality for
    non-x86 targets.

    Move echo output if MAKEFLAGS is empty outside of usage().

    Remove TARGET/TARGET_ARCH evaluation.

  r272380:
    Avoid using env(1) to set values passed to mk-vmimage.sh,
    and instead pass the values as arguments to the script,
    making it easier to run this by hand, without 'make release'.

    Add usage_vm_base() and usage_vm_image() usage helpers.

  r272381:
    After evaluating WITH_VMIMAGES is non-empty, ensure
    the mk-vmimage.sh script exists before running it.

  r272392:
    Add WITH_COMPRESSED_VMIMAGES variable, which when set enables
    xz(1) compression of the virtual machine images.

    This is intentionally separate to allow more fine-grained
    tuning over which images are compressed, especially in cases
    where compressing 20GB sparse images can take hours.

  r272412:
    Document the new 'vm-image' target, and associated release.conf
    variables.

  r272413:
    Remove two stray comments added during the initial iterations
    of testing, no longer needed.

Sponsored by:	The FreeBSD Foundation
Update the FreeBSD versions in the stable/10 errata documentation
to reflect reality.

Approved by:	re (implicit)
Sponsored by:	The FreeBSD Foundation
Clean up the stable/10 errata document now that releng/10.1
has precedence over releng/10.0.

Approved by:	re (implicit)
Sponsored by:	The FreeBSD Foundation
Revert r273084:
  In the stable/ branches, release.prev intentionally points to the
  previous version, in addition to a number of intentional version
  mappings for the errata.html page, that this commit breaks.

Reported by:	hrs
Approved by:	re (implicit)
Sponsored by:	The FreeBSD Foundation
MFC r269627:

Mention tmpfs(5)

PR:             192389
Submitted by:   yaneurabeya@gmail.com
Approved by:    hrs (mentor)
MFC r269023,r272503,r272505,r272523,r272567,r272569,r272574

Prepare fget_unlocked for reading fd table only once.

Some capsicum functions accept fdp + fd and lookup fde based on that.
Add variants which accept fde.

===============================

Add sequence counters with memory barriers.

Current implementation is somewhat simplistic and hackish,
will be improved later after possible memory barrier overhaul.

===============================

Plug capability races.

fp and appropriate capability lookups were not atomic, which could result in
improper capabilities being checked.

This could result either in protection bypass or in a spurious ENOTCAPABLE.

Make fp + capability check atomic with the help of sequence counters.

===============================

Put and #ifdef _KERNEL around the #include for opt_capsicum.h to
hopefully allow the build to finish after r272505.

===============================

filedesc: fix up breakage introduced in 272505

Include sequence counter supports incoditionally [1]. This fixes reprted build
problems with e.g. nvidia driver due to missing opt_capsicum.h.

Replace fishy looking sizeof with offsetof. Make fde_seq the last member in
order to simplify calculations.

===============================

Keep struct filedescent comments within 80-char limit.

===============================

seq_t needs to be visible to userspace
MFC r267851:

Continue the crusade towards a dev_clone()-free kernel, removing its
usage from dtrace. The dtrace code already uses cdevpriv(9) since FreeBSD
8, so this change is quite harmless.

Originally by:	davide
Reviewed by:	markj
MFC r272749:
  Fix comment.
MFC r272756:  Properly report 12Gbps connection rate.

Reviewed by:	kadesai, slm
MFC r272069:
Switch the defaults to not split the RLIMIT_STACK-sized initial thread
stack into the stacks of the created threads.  Add knob
LIBPTHREAD_SPLITSTACK_MAIN to restore the older behaviour.
MFC r272070:
Expand the libthr(3) manpage to document knobs accepted by libthr.so
and explain some internal working of the library, neccessary to
understand the knobs effects.

MFC r272153 (by pluknet):
Fix description of mutex acquisition.