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

Fix some way-past-brucification complaints from FlexeLint.

Quiet warnings about mis-matched pointer assignment.

Tested on: PowerPC

Pointy hat commit:

Don't Cut&Paste from big endian to little endian function without subsequent
adjustments.

Use "unsigned char" instead of "u_char" to avoid trouble.

Add inline functions {be,le}{16,32,64}{enc,dec}() for encoding decoding
into byte strings of unknown alignment.

Make this header self-reliant with regard to the types it uses.

Move the new byte order function prototypes from <sys/param.h> to
<sys/endian.h>. This puts us in line with NetBSD and OpenBSD.