[PATCH] Add 'bs_unaligned' option

If this is specified with 'bsrange', fio will use any byte size value
in the bs range for an io unit buffer length. Normally fio defaults to
using a multiple of the minimum bs size, as that is required for any
type of raw io.

Signed-off-by: Jens Axboe <jens.axboe@oracle.com>