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
3a3d912cfc