Adding a primer for the standard module Random.

This primer intentionally does not include any functionality with Private in
the name.  It also does not include the SeedGenerators record, as that record
only includes our default random generator settings.
There are too many future effort indications in the Random module 
today.  Hopefully when they get resolved, we can just include a pointer 
to the module.

On 09/16/2014 04:51 PM, Vassily Litvinov wrote:
>
> In test/release/examples/primers/random.chpl:
>
> > @@ -0,0 +1,138 @@
> > +/*
> > + * Standard Module: Random primer
> > + *
> > + * This primer demonstrates usage of the standard module Random.chpl.
> > + *
> > + */
> > +
> > +use Random;
> > +
> > +//
> > +// This module contains a random number generator based on
> > +// the one used in the NPB benchmarks.  Tailoring the NPB comments to
> > +// this code, we can say the following:
> > +//
>
> Ideally redirect to this text in the Random module itself.
> For now OK to have it here.
>
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> <https://github.com/chapel-lang/chapel/pull/449/files#r17638031>.
>