* lib/human.c, lib/human.h (human_readable): Coalesce last two args
into one, for convenience. All callers changed.
(human_block_size): New function.
* lib/human.c: Include <config.h> only if HAVE_CONFIG_H.
Include <stdlib.h> if HAVE_STDLIB_H;
declare getenv unless HAVE_DECL_GETENV.
(_): New macro.
Include <argmatch.h>, <error.h>, <xstrtoul.h>.
(DEFAULT_BLOCK_SIZE): New macro.
(block_size_args, block_size_types): New constants.
(humblock): New function.