stand: 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

Remove $FreeBSD$: one-line .c pattern

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

Adjust parse() definition in boot2 to avoid clang 15 warning

With clang 15, the following -Werror warning is produced:

stand/i386/boot2/boot2.c:358:6: error: a function declaration without a prototype is deprecated in all versions of C [-Werror,-Wstrict-prototypes]

This is because parse() is declared with a (void) argument list, and
defined with an empty argument list. Make the definition match the
declaration.

MFC after: 3 days

Further style(9) changes.

Tested by: objdump -d | md5 (both in-tree clang and lang/gcc6)

Purely whitespace changes bringing this file closer to style(9).

Curiously, changing whitespace seems to cause the md5 of the .o files to differ
these days hence the following testing strategy:

Tested by: objdump -d | md5 (both in-tree clang and lang/gcc6)

Revert r329269.

I tried to rework a section to fit inside 80 columns but the change ended
up being functional. Back this out so I can readdress.

Reformat to come significantly closer to style(9).

Reviewed by: imp, jhibbits
Differential Revision: https://reviews.freebsd.org/D14366

Move sys/boot to stand. Fix all references to new location

Sponsored by: Netflix