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

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

Major cleanup:

- add __unused where appropriate
- PAM_RETURN -> return since OpenPAM already logs the return value.
- make PAM_LOG use openpam_log()
- make PAM_VERBOSE_ERROR use openpam_get_option() and check flags
for PAM_SILENT
- remove dummy functions since OpenPAM handles missing service
functions
- fix various warnings

Sponsored by: DARPA, NAI Labs

Three times lucky: <stddef.h>, not <sys/param.h>

Oops, the correct header to include for NULL is <sys/param.h>.

#include <sys/types.h> for NULL (hidden by Linux-PAM header pollution)

Sponsored by: DARPA, NAI Labs

#include cleanup.

Sponsored by: DARPA, NAI Labs

WARNS=4 fixes. Protect with NO_WERROR for the modules that have
warnings that are hard to fix or that I've been asked to leave alone.

Add __FBSDID()s to libpam

Clean up (and in some cases write) the PAM mudules, using
o The new options-processing API
o The new DEBUG-logging API

Add man(1) pages for ALL modules. MDOC-Police welcome
to check this.

Audit, clean up while I'm here.