[fortran, doc] Improve random_seed example

[Steve Kargl]

On Fri, May 17, 2013 at 03:18:01PM +0300, Janne Blomqvist wrote:
> Hi,
> 
> the example we provide for the usage of the random_seed intrinsic
> could be better. At least one user has already been tripped over by
> the fact that on some targets the first call to system_clock returns
> 0, resulting in a poor seed. Below is an improved(?!) example program.
> 
> Ok for trunk/4.8/4.7? (Changelog + patch is of course trivial once
> there is agreement on the code itself)
> 

Looks OK to me.

It should probably also be noted in the manual that one can get
real poor results if one does not set all seed values.

-- 
Steve