Document sleep button, lid status and lidaction/pwraction support

landry added the sensor back in 2013 and suspend via sleep button also works
(at least on ThinkPads).

`machdep.{lid,pwr}action' are super useful but only mentioned in
/etc/examples/wsconsctl.conf providing poor discovery.

acpibtn(4) is the most prominent driver supporting them, so document their
behaviour here as a reference point (`man -k .=lidaction' now shows it).

suspend/hibernate wording is taken from apm(8).
sysctl value list style is taken from sysctl(2)'s KERN_POOL_DEBUG.

Feedback jmc

use .Mt for email addresses; from Jan Stary <hans at stare dot cz>; ok jmc@

machdep.kbdreset enables a shutdown by Ctrl-Alt-Del on amd64 and
i386. Stop abusing it on other archs for controling a shutdown by
pressing the soft power button:

* Add a MI sysctl hw.allowpowerdown; if set to 1 (the default) it
allows a power button shutdown.
* Make acpi(4)/acpibtn(4) honor hw.allowpowerdown.
* Switch the various power button intercepts on landisk, sgi, sparc64
and zaurus over to hw.allowpowerdown.
* Garbage collect the machdep.kbdreset sysctl on all archs other than
amd64 and i386.

ok miod@

convert to new .Dd format;

- add a list in acpi.4 of all acpi devices which attach
- make the .Nd a little nicer whilst here

help/ok mk

As requested by deraadt, split acpi(4) up into individual driver pages.

While doing this, improve and add the text of some manuals. Some of
these are simply revived versions of the pages back from when they were
individual pages.

Input and ok from jmc.

Note: When we wrote these pages, people submitted new pages to jmc and
I. At some point during this, we decided to merge all pages into acpi(4)
(which is now being undone), and I lost track of who sent what. Thus,
if you think you should be the copyright owner of any of these files,
get back to me in private.

use .Mt for email addresses; from Jan Stary <hans at stare dot cz>; ok jmc@

machdep.kbdreset enables a shutdown by Ctrl-Alt-Del on amd64 and
i386. Stop abusing it on other archs for controling a shutdown by
pressing the soft power button:

* Add a MI sysctl hw.allowpowerdown; if set to 1 (the default) it
allows a power button shutdown.
* Make acpi(4)/acpibtn(4) honor hw.allowpowerdown.
* Switch the various power button intercepts on landisk, sgi, sparc64
and zaurus over to hw.allowpowerdown.
* Garbage collect the machdep.kbdreset sysctl on all archs other than
amd64 and i386.

ok miod@

convert to new .Dd format;

- add a list in acpi.4 of all acpi devices which attach
- make the .Nd a little nicer whilst here

help/ok mk

As requested by deraadt, split acpi(4) up into individual driver pages.

While doing this, improve and add the text of some manuals. Some of
these are simply revived versions of the pages back from when they were
individual pages.

Input and ok from jmc.

Note: When we wrote these pages, people submitted new pages to jmc and
I. At some point during this, we decided to merge all pages into acpi(4)
(which is now being undone), and I lost track of who sent what. Thus,
if you think you should be the copyright owner of any of these files,
get back to me in private.