bug#6658: [PATCH] randread: don't require -lrt

[Jim Meyering]

Paul Eggert wrote:
> In looking at the random part of coreutils some more, I see some
> issues.
>
> 1.  Apps that use random numbers typically must link to -lrt,
>     for a very small benefit (nanosecond resolution rather than
>     microsecond resolution time stamp for random seed).  Often
>     this "benefit" is illusory as the time stamps really are not
>     nanosecond resolution.
>
> 2.  If /dev/urandom is available, it should be used to seed
>     the ISAAC generator.  This will cost more than invoking
>     gettimeofday() but it's far more random.
>
> 3.  We could get about 2X CPU performance on 64-bit machines by using
>     ISAAC64 instead of ISAAC.
>
> The patch below implements (1); I haven't installed it.  I'd like to
> do (2) and (3) too, but thought I'd ask for feedback first.

These are all welcome changes, and the patch for (1) looks fine.
Thanks!