Revert r330897:

This was intended to be a non-functional change. It wasn't. The commit
message was thus wrong. In addition it broke arm, and merged crypto
related code.

Revert with prejudice.

This revert skips files touched in r316370 since that commit was since
MFCed. This revert also skips files that require $FreeBSD$ property
changes.

Thank you to those who helped me get out of this mess including but not
limited to gonzo, kevans, rgrimes.

Requested by: gjb (re)

Partial merge of the SPDX changes

These changes are incomplete but are making it difficult
to determine what other changes can/should be merged.

No objections from: pfg

MFC r319969-r319970

r319969:
Use nitems() from sys/param.h.

r319970:
Use nitems() from sys/param.h.

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

Stop including if_var.h from userland.

Sponsored by: Nginx, Inc.

More -Wmissing-variable-declarations fixes.

In addition to adding `static' where possible:

- bin/date: Move `retval' into extern.h to make it visible to date.c.
- bin/ed: Move globally used variables into ed.h.
- sbin/camcontrol: Move `verbose' into camcontrol.h and fix shadow warnings.
- usr.bin/calendar: Remove unneeded variables.
- usr.bin/chat: Make `line' local instead of global.
- usr.bin/elfdump: Comment out unneeded function.
- usr.bin/rlogin: Use _Noreturn instead of __dead2.
- usr.bin/tset: Pull `Ospeed' into extern.h.
- usr.sbin/mfiutil: Put global variables in mfiutil.h.
- usr.sbin/pkg: Remove unused `os_corres'.
- usr.sbin/quotaon, usr.sbin/repquota: Remove unused `qfname'.

Fix alignment related warnings reported by gcc
Switch from old style arguments to modern C
remove WARNS as a result

tested with "make universe"

Approved by: cperciva
MFC after: 1 week

Cleanup of userland __P use

when no source-address-selection policy is installed, not scan
the sysctl MIB, as it leads to an unnecessary sysctl error.

Obtained from: KAME

fixed a bug that 'ip6addrctl delete' command does not work

obtained from: KAME

add ip6addrctl(8) which is a command to configure address
selection policy for IPv6 and IPv4 described in RFC3484.
source address selection part of RFC3484 is not merged
from KAME, yet.

Obtained from: KAME