random(4) plugin infrastructure for mulitple RNG in a modular fashion

[Steve Kargl]

On Wed, Aug 07, 2013 at 11:28:58AM -0700, David O'Brien wrote:
> 
> * Make Yarrow an optional kernel component -- enabled by "YARROW_RNG"
>   option.  The files sha2.c, hash.c, randomdev_soft.c and yarrow.c
>   comprise yarrow.  random(4) device doesn't really depend on
>   rijndael-*.  Yarrow, however, does.
> 
> * If the kernel doesn't have any random_adaptor adapters present then
>   the creation of /dev/random is postponed until next random_adaptor
>    is kldload'ed.

My kernel config files have included the following 2 lines for
ages:

makeoptions  NO_MODULES
device       random

If I try to build a new kernel under your scheme, will the
build die with an error about a missing option?  If the answer
is 'no', then the yarrow adaptor should be opt-out.

-- 
steve