lockstat: Use gelf.h instead of playing games with the preprocessor

This reverts a portion of 1477dd823ee ("Merge OpenZFS support in to
HEAD."). No functional change intended.

MFC after: 1 week

Merge OpenZFS support in to HEAD.

The primary benefit is maintaining a completely shared
code base with the community allowing FreeBSD to receive
new features sooner and with less effort.

I would advise against doing 'zpool upgrade'
or creating indispensable pools using new
features until this change has had a month+
to soak.

Work on merging FreeBSD support in to what was
at the time "ZFS on Linux" began in August 2018.
I first publicly proposed transitioning FreeBSD
to (new) OpenZFS on December 18th, 2018. FreeBSD
support in OpenZFS was finally completed in December
2019. A CFT for downstreaming OpenZFS support in
to FreeBSD was first issued on July 8th. All issues
that were reported have been addressed or, for
a couple of less critical matters there are
pull requests in progress with OpenZFS. iXsystems
has tested and dogfooded extensively internally.
The TrueNAS 12 release is based on OpenZFS with
some additional features that have not yet made
it upstream.

Improvements include:
project quotas, encrypted datasets,
allocation classes, vectorized raidz,
vectorized checksums, various command line
improvements, zstd compression.

Thanks to those who have helped along the way:
Ryan Moeller, Allan Jude, Zack Welch, and many
others.

Sponsored by: iXsystems, Inc.
Differential Revision: https://reviews.freebsd.org/D25872

Rework and simplify the ksyms(4) implementation.

- Store the symbol table contents in an anonymous swap-backed object. Have
mmap(/dev/ksyms) map that object, and stop mapping the symbol table into
the calling process in ksyms_open(). Previously we would cache a pointer
to the pmap of the opening process, and mmap(/dev/ksyms) would create a
mapping using the physical address found by a pmap lookup at the initial
mapping address. However, this assumes that the cached pmap is valid,
which may not be the case. [1]
- Remove the ksyms ioctl interface. It appears to have been added to work
around a limitation in libelf that no longer exists; see r321842.
Moreover, the interface is difficult to support and isn't present in
illumos. Since ksyms was added specifically to support lockstat(1), it
is expected that this removal won't have any real impact.
- Simplify ksyms_read() to avoid unnecessary copying.
- Don't call the device handle destructor if we fail to capture a snapshot
of the kernel's symbol table. devfs will do that for us.

Reported by: Ilja van Sprundel <ivansprundel@ioactive.com> [1]
Reviewed by: kib (previous revision)
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D11789

Remove local variables missed in r321842.

X-MFC with: r321842

Let lockstat use ksyms(4)'s mmap interface.

The workaround described in the deleted comment is no longer needed.

MFC after: 1 week

Mechanically convert cddl sun #ifdef's to illumos

Since the upstream for cddl code is now illumos not sun, mechanically
convert all sun #ifdef's to illumos #ifdef's which have been used in all
newer code for some time.

Also do a manual pass to correct the use if #ifdef comments as per style(9)
as well as few uses of #if defined(__FreeBSD__) vs #ifndef illumos.

MFC after: 1 month
Sponsored by: Multiplay

Include two headers to provide prototype for modfind(2) and kldload(2).

MFC after: 2 weeks

If the initial attempt to open /dev/ksyms fails, kldload the ksyms module
and retry.

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Create the altix project branch. The altix project will add support
for the SGI Altix 350 to FreeBSD/ia64. The hardware used for porting
is a two-module system, consisting of a base compute module and a
CPU expansion module. SGI's NUMAFlex architecture can be an excellent
platform to test CPU affinity and NUMA-aware features in FreeBSD.

Add the OpenSolaris lockstat(1M) command. Requires the dtrace driver,
the lockstat provider, and the ksyms(4) pseudo driver kernel modules.

Approved by: gnn (mentor)