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/

geli: style nits

geli: partially revert r348709

Let's change the unsigned arguments to the signed one, but let's don't
change pointers to the array notation.

Requested by: pjd

geli: build warning fixes

Submitted by: Aaron Prieger <aprieger@llnw.com>
Reviewed by: sbruno
Differential Revision: https://reviews.freebsd.org/D11068

When building standalone, include stand.h rather than the kernel
includes or the userland includes.

Sponsored by: Netflix

improve PBKDF2 performance

The PBKDF2 in sys/geom/eli/pkcs5v2.c is around half the speed it could be

GELI's PBKDF2 uses a simple benchmark to determine a number of iterations
that will takes approximately 2 seconds. The security provided is actually
half what is expected, because an attacker could use the optimized
algorithm to brute force the key in half the expected time.

With this change, all newly generated GELI keys will be approximately 2x
as strong. Previously generated keys will talk half as long to calculate,
resulting in faster mounting of encrypted volumes. Users may choose to
rekey, to generate a new key with the larger default number of iterations
using the geli(8) setkey command.

Security of existing data is not compromised, as ~1 second per brute force
attempt is still a very high threshold.

PR: 202365
Original Research: https://jbp.io/2015/08/11/pbkdf2-performance-matters/
Submitted by: Joe Pixton <jpixton@gmail.com> (Original Version), jmg (Later Version)
Reviewed by: ed, pjd, delphij
Approved by: secteam, pjd (maintainer)
MFC after: 2 weeks
Differential Revision: https://reviews.freebsd.org/D8236

Make additional parts of sys/geom/eli more usable in userspace

The upcoming GELI support in the loader reuses parts of this code
Some ifdefs are added, and some code is moved outside of existing ifdefs

The HMAC parts of GELI are broken out into their own file, to separate
them from the kernel crypto/openssl dependant parts that are replaced
in the boot code.

Passed the GELI regression suite (tools/regression/geom/eli)
Files=20 Tests=14996
Result: PASS

Reviewed by: pjd, delphij
MFC after: 1 week
Sponsored by: ScaleEngine Inc.
Differential Revision: https://reviews.freebsd.org/D4699