Make `loc` and `scale` arguments of rvs_normal optional when returning an array

[Beliavsky]

I wish the loc and scale arguments of rvs_normal were optional when generating a 1D array of variates, so that one could write

x = rvs_normal(array_size=n)

instead of

x = rvs_normal(0.0_dp, 1.0_dp, array_size=n)

That is how numpy.random.normal works.