These sys/cdefs.h are not needed. Purge them. They are mostly left-over
from the $FreeBSD$ removal. A few in libc are still required for macros
that cdefs.h defines. Keep those.
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D42385
(cherry picked from commit 559a218c9b)
As per the updated FreeBSD copyright template. These were unambiguous
cases where the Foundation was the only listed copyright holder.
Sponsored by: The FreeBSD Foundation
