MFC r256317:
Fix mode page length calculation to remove last garbage line from the
`camcontrol mode daX -l` output.
MFC r256750:
Improve XHCI stability. When a command timeout happens, the command
should be aborted else the command queue can stop. Refer to section
"4.6.1.2" of the XHCI specification.
MFC r253816: MFV r253780:

To quote Illumos #3875:

The problem here is that if we ever end up in the error
path, we drop the locks protecting access to the zfsvfs_t
prior to forcibly unmounting the filesystem. Because z_os
is NULL, any thread that had already picked up the zfsvfs_t
and was sitting in ZFS_ENTER() when we dropped our locks
in zfs_resume_fs() will now acquire the lock, attempt to
use z_os, and panic.

Illumos ZFS issues:
  3875 panic in zfs_root() after failed rollback
MFC r256646, r256767, r257038:
  When installing updates, install new directories first and remove old
  directories last.

  Allow ~ in file names so libtool droppings in contrib don't break updates.
  It has happened twice now, and is likely to happen again.

  Be more selective when filtering for lib*.so.N files.  These are deleted
  at the end of the upgrade process, after warning users to upgrade any
  3rd party software (e.g., from the ports tree) which might link to the
  libraries being removed.

Errata Notice:  FreeBSD-EN-13:04.freebsd-update
MFC r257151:

  Document /var/cache/pkg into hier(7) which pkg(8) uses.

Approved by:	bapt
MFC r257206:
Fix a deadlock when trying to power off a USB device. The deadlock
happens because the code in question is trying to modify the parent
USB port registers outside the USB explore thread.