yarrow_fast_reseed) and made non-static. Don't generate seed file
here, let the application use yarrow256_random instead.
(yarrow256_slow_reseed): Renamed (was yarrow_slow_reseed) and made
non-static.
(yarrow256_force_reseed): Deleted function, use
yarrow256_slow_reseed instead. For backwards compatibility,
yarrow.h defines yarrow256_force_reseed as an alias for that
function.

* yarrow.h (struct yarrow256_ctx): Deleted seed_file buffer.

Rev: nettle/yarrow.h:1.2
Rev: nettle/yarrow256.c:1.4