MFC r325834,r325997,326502: Move sys/boot to stand/

This is effectively a direct commit to stable/11, due to differences between
stable/11 and head. Changes to DTS in sys/boot/fdt/dts were often
accompanied by kernel changes. Many of these were also risc-v updates that
likely had many more dependencies to MFC.

Because of this, sys/boot/fdt/dts remains as-is while everything else in
sys/boot relocates to stand/.

r325834: Move sys/boot to stand. Fix all references to new location

r325997: Remove empty directories.

r326502: Document the sys/boot -> stand move in hier.7 and the top-level README.

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

Remove unused includes.

Remove support for autoloading ACPI from the loader. Leave in the code to
detect ACPI and export info such as the location of the RSDP via hints as
that is still useful.

Use __FBSDID().
Also some minor copyright style cleanups.

Revert leftover AMD64 disable-acpi-module stuff.

ACPI will always be present on AMD64 - it will never be an autodetect
module.

Parse hint.acpi.0.disabled correctly.
Now that hint.acpi.0.disabled="0" won't disable acpi as expected.

Pointed-out by: bde

s/hint.acpi.0.disable/hint.acpi.0.disabled/

Fix device hints entry for disabling acpi(4).
This also should fix the arbitration with apm(4) when both drivers
are enabled.

Note that your /boot/device.hints needs to be updated if you want to
stop auto-loading acpi.ko or disable acpi(4).

Restore autoloading of ACPI module.

Document the approved ways of disabling it.
Submitted by: Daniel O'Connor <doconnor@gsoft.com.au>

Don't auto load ACPI -- it causes trouble with my laptop and is TOTALLY
undocumented how to control its loading and queries to freebsd-current
go unanswered.

Implement the long-awaited module->file cache database. A userland
tool (kldxref(8)) keeps a cache of what modules and versions are inside
what .ko files. I have tested this on both Alpha and i386.

Submitted by: bp

Teach the loader how to find the system ACPI information, and autoload
the ACPI module if the system apperars to be ACPI compliant.

This is an initial cut; the load should really be done by Forth support
code, and we should check both the BIOS build date and a blacklist.

$Id$ -> $FreeBSD$

Bootloader update.

- Implement a new copyin/readin interface for loading modules.
This allows the module loaders to become MI, reducing code duplication.
- Simplify the search for an image activator for the loaded kernel.
- Use the common module management code for all module metadata.
- Add an 'unload' command that throws everything away.
- Move the a.out module loader to MI code, add support for a.out
kld modules.

Submitted by: Alpha changes fixed by Doug Rabson <dfr@freebsd.org>

This commit was generated by cvs2svn to compensate for changes in r38465,
which included commits to RCS files with non-trunk default branches.

This is the new unified bootstrap, sometimes known previously as the
'three-stage' bootstrap.
There are a number of caveats with the code in its current state:
- The i386 bootstrap only supports booting from a floppy.
- The kernel and kld do not yet know how to deal with the extended
information and module summary passed in.
- PnP-based autodetection and demand loading of modules is not implemented.
- i386 ELF kernel loading is not ready yet.
- The i386 bootstrap is loaded via an ugly blockmap.

On the alpha, both net- and disk-booting (SRM console machines only) is
supported. No blockmaps are used by this code.

Obtained from: Parts from the NetBSD/i386 standalone bootstrap.