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spdx: The BSD-2-Clause-FreeBSD identifier is obsolete, drop -FreeBSD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

uefisign: fix handling of errors from child proc

Close the unused pipe file descriptors so the parent will notice if
the child exits prematurely. Previously, the parent would block
forever on a read from the pipe.

$ uefisign -c foo.cert -k foo.key -o loader.efi loader.efi.unsigned
uefisign: section points inside the headers
load: 0.06 cmd: uefisign 4502 [piperd] 7.25r 0.00u 0.00s 0% 5968k
... _sleep+0x1be pipe_read+0x3d6 kern_readv+0x8c sys_read+0x83 ...

Reviewed by: trasz
MFC after: 1 week
Sponsored by: Dell EMC Isilon
Differential Revision: https://reviews.freebsd.org/D29605

usr.sbin/uefisign: prevent specifying certificate, key or output
multiple times.

MFC after: 1 month

Drop "All rights reserved" from all my stuff. This includes
Foundation copyrights, approved by emaste@. It does not include
files which carry other people's copyrights; if you're one
of those people, feel free to make similar change.

Reviewed by: emaste, imp, gbe (manpages)
Differential Revision: https://reviews.freebsd.org/D26980

Make uefisign(8) buildable.

Add SPDX identifiers for uefisign(8) sources.

MFC after: 2 weeks

Add uefisign(8), UEFI Secure Boot signing utility.

MFC after: 1 month
Sponsored by: The FreeBSD Foundation