illumos gate

FreeBSD updates:
r345066

    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.

347393
    loader: use DPRINTF in biosdisk.c and define safe DPRINTF

    r345066 did miss biosdisk.c.

    Also define DPRINTF as ((void)0) for case we do not want debug printouts.