libc: Purge unneeded cdefs.h

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

Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

libc: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using mis-identified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

Create the altix project branch. The altix project will add support
for the SGI Altix 350 to FreeBSD/ia64. The hardware used for porting
is a two-module system, consisting of a base compute module and a
CPU expansion module. SGI's NUMAFlex architecture can be an excellent
platform to test CPU affinity and NUMA-aware features in FreeBSD.

- Import the HEAD csup code which is the basis for the cvsmode work.

Add __FBSDID() tags.

MFC after: 3 days

Minor white space tweak.

MFC after: 3 days

Implement mac_get_peer(3) using getsockopt() with SOL_SOCKET and
SO_PEERLABEL. This provides an interface to query the label of a
socket peer without embedding implementation details of mac_t in
the application. Previously, sizeof(*mac_t) had to be specified
by an application when performing getsockopt().

Document mac_get_peer(3), and expand documentation of the other
mac_get(3) functions. Note that it's possible to get EINVAL back
from mac_get_fd(3) when pointing it at an inappropriate object.

NOTE: mac_get_fd() and mac_set_fd() support for sockets will
follow shortly, so the documentation is slightly ahead of the
code.

Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories

Eliminate 61 warnings emitted at WARNS=2 (leaving 53 to go).
Only warnings that could be fixed without changing the generated object
code and without restructuring the source code have been handled.

Reviewed by: /sbin/md5

Reflect MAC kernel/user API changes into the libc MAC implementation.
This removes a lot of complexity, since we basically just reserve
space on a retrieval of a label, and pass around strings. Two new
elements: (1) consumers of the API must now declare what label
elements they are interested in retrieving, or (2) rely on the default
provided in a new configuration file, mac.conf.

Approved by: re
Obtained from: TrustedBSD Project
Sponsored by: DARPA, Network Associates Laboratories

Introduce support for Mandatory Access Control and extensible
kernel access control.

Extensions to libc to provide basic MAC label manipulation facilities
for userland. These interface will be replaced in the next month
or two with more flexible interfaces, but provide sufficient support
to allow use of the Biba and MLS policies for user applications.

libc_r wrappers to follow.

Obtained from: TrustedBSD Project
Sponsored by: DARPA, NAI Labs