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

Remove NetBSD Foundation clauses 3 & 4. They eliminated those clauses
last year.

Add getopt_long_only()

In the comment tell about optreset extension for NetBSD ghetopt_long()

Add optreset to getopt.h too since NetBSD getopt_long() (but not GNU one)
use it too.

Try to better mimic GNU getopt.h which does not assume to make visible
all unistd.h functions, use _GETOPT_DECLARE define for that.

Fix comment: GNU getopt.h to which this header tries to mimic does not declare
getsubopt/optreset

Add getopt_long(3).

Obtained from: NetBSD
Sponsored by: Apple