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

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

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

Include paths.h for prototype of getbootfile(3).

Return "/boot/kernel/kernel" instead of "/kernel" if the sysctl() call
fails. The documentation was incorrectly updated in getbootfile.3 rev. 1.10.

Fix SCM ID's.

$Id$ -> $FreeBSD$

Revert $FreeBSD$ to $Id$

Make the long-awaited change from $Id$ to $FreeBSD$

This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.

Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.

If sysctl() fails, return "/kernel" so as not to screw people who haven't
updated their kernels yet.

Added getbootfile(3), for an easy C interface to the kern.bootfile MIB
variable. This one's even documented!