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

Include a couple of headers to ensure consistency between the prototype and
the function definition.

Clean out the leftovers from the i386_set_gsbase() TLS conversion.

Like on libthr, there is an i386_set_gsbase() stub implementation here
to avoid libc.so.5 issues. This should likely be a weak symbol and I
expect this will be fixed soon.

Approved by: re

Provide stub functions for i386_set_ldt() and i386_get_ldt() even when
compiling as an amd64 support binary. They will return EINVAL on an amd64
kernel, but this simplifies other #ifdefs that were getting a bit nasty.

No longer use _amd64_set_gsbase(). Use i386_set_gsbase() even when
building for amd64.

Attempt i386_set_gsbase() before using the user_ldt code. Unimplemented
sysarch() calls return EINVAL, not SIGSYS.. so we can trivially adapt.

When building the custom i386 libraries for use on amd64 kernels, we
can't use the i386_set_ldt() family of routines, because they are not
implemented. Instead, use the recently exposed direct access sysarch
routines for setting what %fs and %gs point to.

Use this for the i386 TLS _set_tp() routine, but only when compiling to
run as a 32 bit support binary for amd64 kernels.

Add support for TLS in statically linked programs.