Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Added ZFS TRIM support which is enabled by default. To disable
ZFS TRIM support set vfs.zfs.trim.enabled=0 in loader.conf.

Creating new ZFS pools and adding new devices to existing pools
first performs a full device level TRIM which can take a significant
amount of time. The sysctl vfs.zfs.vdev.trim_on_init can be set to 0
to disable this behaviour.

ZFS TRIM requires the underlying device support BIO_DELETE which
is currently provided by methods such as ATA TRIM and SCSI UNMAP
via CAM, which are typically supported by SSD's.

Stats for ZFS TRIM can be monitored by looking at the sysctl's
under kstat.zfs.misc.zio_trim.

MFC r240868: Add TRIM support
MFC r244155: Renamed zfs trim stats
MFC r244187: Upgrade TRIM free request sizes optimisation
MFC r244188: Added vfs.zfs.vdev.trim_on_init sysctl
MFC r248572: Add TRIM support for L2ARC
MFC r248574: Improve TXG handling in the TRIM module
MFC r248575: TRIM cache devices based on time instead of TXGs
MFC r248576: Names the ZFS TRIM thread
MFC r248577: Optimisation of TRIM processing
MFC r248602: Fix for building libzpool under i386
MFC r249921: Enabled ZFS TRIM by default

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Introduce signed and unsigned version of CTLTYPE_QUAD, renaming
existing uses. Rename sysctl_handle_quad() to sysctl_handle_64().

Forced commit to note that these files were repo copied.

Despite several examples in the kernel, the third argument of
sysctl_handle_int is not sizeof the int type you want to export.
The type must always be an int or an unsigned int.

Remove the instances where a sizeof(variable) is passed to stop
people accidently cut and pasting these examples.

In a few places this was sysctl_handle_int was being used on 64 bit
types, which would truncate the value to be exported. In these
cases use sysctl_handle_quad to export them and change the format
to Q so that sysctl(1) can still print them.

Please welcome ZFS - The last word in file systems.

ZFS file system was ported from OpenSolaris operating system. The code in under
CDDL license.

I'd like to thank all SUN developers that created this great piece of software.

Supported by: Wheel LTD (http://www.wheel.pl/)
Supported by: The FreeBSD Foundation (http://www.freebsdfoundation.org/)
Supported by: Sentex (http://www.sentex.net/)