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

Disable alignment faults on armv6, adjust various alignment-related macros
to match the new state of affairs. The hardware we support has always been
able to do unaligned accesses, we've just never enabled it until now.

This brings FreeBSD into line with all the other major OSes, and should help
with the growing volume of 3rd-party software that assumes unaligned access
will just work on armv6 and armv7.

Adjust _ALIGNBYTES to the proper value for arm and armv6 arches. Modern
compilers can emit arm instructions that require 8-byte alignment. The
alignment-sensitive instructions were added in armv5, which has to be
supported by our combined v4/v5 kernels, so the value is set uncoditionally
for all arm architecture versions.

Also adjust the comment to explain in more detail why the macros have the
form and values they do.

Per advice from bde@, maintain the unsignedness of the value of _ALIGNBYTES
(but do so using his second choice of allowing sizeof() to supply the
unsignedness, rather than just hardcoding '8U', which in my mind would
require an even more verbose comment to explain why it's right). Also
explain in the comment that the resulting type of _ALIGN() is equivelent
to uinptr_t on arm (32-bit unsigned int), but it's purposely spelled as
"unsigned" to avoid problems with including other header files. Even
including machine/_types.h to allow use of __uintptr_t causes compilation
failures because of this header being included (indirectly) in asm code.

The discussion that led to this change (albeit at a glacial pace) is at
https://lists.freebsd.org/pipermail/svn-src-head/2014-November/064593.html

Get rid of the _NO_NAMESPACE_POLLUTION kludge by creating an
architecture specific include file containing the _ALIGN*
stuff which <sys/socket.h> needs.