Move struct bio_set and biovec_slab definitions to bio.h so they can
be used outside of bio.c.
Signed-off-by: NMartin K. Petersen <martin.petersen@oracle.com>
Reviewed-by: NJeff Moyer <jmoyer@redhat.com>
Signed-off-by: NJens Axboe <jens.axboe@oracle.com>