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

Renumber clauses to reduce diffs to other versions

NetBSD, OpenBSD, and Android's Bionic number the clauses 1 through 3,
so follow suit to make comparison easier.

- ANSIfy function definitions
- use nul when we are looking for a terminating character where appropriate

Approved by: imp

Per Regents of the University of Calfornia letter, remove advertising
clause.

# If I've done so improperly on a file, please let me know.

Replace wcsstr() with an implementation based on strstr(), which is far
more efficient. The problem with the previous implementation was that it
calculated the length of the first argument ("big") with wcslen() when
it was not necessary.

Remove unnecessary #include <assert.h>; it was used to bring in the
_DIAGASSERT macro on NetBSD, but we don't need it.

Add restrict qualifiers where C99 permits them. All of these already had
restrict qualifiers on their prototypes in <wchar.h>.

Fix the style of the SCM ID's.
I believe have made all of libc .c's as consistent as possible.

rcsid[]->__FBSDID

Make the rcsid and FreeBSD IDs more sane in the wcs* and wmem* files.
Do the same for the non-wcs*/wmem* files while I'm here.

Unbreak world; _DIAGASSERT macro is not available in FreeBSD.

initial import of locale insensitive wcs* and wmem* functions.

Obtained from: NetBSD and Citrus.