sys: Automated cleanup of cdefs and other formatting

Apply the following automated changes to try to eliminate
no-longer-needed sys/cdefs.h includes as well as now-empty
blank lines in a row.

Remove /^#if.*\n#endif.*\n#include\s+<sys/cdefs.h>.*\n/
Remove /\n+#include\s+<sys/cdefs.h>.*\n+#if.*\n#endif.*\n+/
Remove /\n+#if.*\n#endif.*\n+/
Remove /^#if.*\n#endif.*\n/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/types.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/param.h>/
Remove /\n+#include\s+<sys/cdefs.h>\n#include\s+<sys/capsicum.h>/

Sponsored by: Netflix

sys: Remove $FreeBSD$: one-line .c pattern

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

spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD

The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.

Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix

sys: general adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified 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.

No functional change intended.

sys/net*: minor spelling fixes.

No functional change.

Fix panic due to page faults while in kernel mode, under conditions of
VM pressure. The reason is that in some codepaths pointers to stack
variables were passed from one thread to another.

In collaboration with: pho
Reported by: pho's stress2 suite
Sponsored by: iXsystems inc.

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

Switch to our preferred 2-clause BSD license.

Approved by: bp

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

/* -> /*- for license, minor formatting changes

size_t != int. Make this compile on 64 bit platforms (eg: amd64).
Also, "u_short value; if (value > 0xffff)" can never be true.

Use __FBSDID().

Add missing #include <sys/mbuf.h>

Permit an empty username which is useful for browsing.

Import kernel part of SMB/CIFS requester.
Add smbfs(CIFS) filesystem.

Userland part will be in the ports tree for a while.

Obtained from: smbfs-1.3.7-dev package.