libsa: Remove redundant sys/cdefs.h

Sponsored by: Netflix

Remove $FreeBSD$: one-line .c pattern

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

Stop setting PG_U in bootstrap mappings.

These mappings are never visible to userspace as they get replaced when
the amd64 pmap is bootstrapped, but there is no need to set PG_U in the
first place.

Reviewed by: alc, kib
MFC after: 1 week
Sponsored by: The FreeBSD Foundation
Differential Revision: https://reviews.freebsd.org/D24547

stand: Improve some debugging experience

Some of these files using <FOO>_DEBUG defined a DEBUG() macro to serve as a
debug-printf. -DDEBUG is useful to enable some debugging output across
multiple ELF/common parts, so switch the DEBUG-as-printf macros over to
something more like DPRINTF that is more commonly used for this kind of
thing and less likely to conflict.

userboot/elf64_freebsd debugging also assumed %llx for uint64; use PRIx64
instead.

MFC after: 1 week

Prefer uintXX_t to u_intXX_t

A foolish consistency is the hobgoblin of little minds, adored by
little statesmen and philosophers and divines. With consistency a
great soul has simply nothing to do. -- Ralph Waldo Emerson

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

Sponsored by: Netflix