Make use of the physical random number accessed by the RdRand
instruction in recent Intel CPUs (Ivy Bridge and later). This library defines the user_unif_rand symbol and gives back a
random number of RdRand.
`hasRDRAND' returns either RdRand available by executing the CPUID.
if HasRDRAND return false of library load time, it does not change
the RNGkind.
if you do changed RNGkind("user") by manual operation
and RdRand is not available, you get NaN.
If you want to detach, it will be set to RNGkind of "default".