This patch changes the device behind /dev/random to start using FreeBSD Yarrow
CPRNG algorithm. Similar to FreeBSD, our /dev/urandom was created as an alias
to /dev/random.
The device operations are linked to Yarrow through the random adaptor API.

Signed-off-by: Raphael S. Carvalho <raphaelsc@cloudius-systems.com>
Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>