Remove x86_64 dependency

[Kezii]

It'd be great if the hard dependency on x86_64 was removed, and a cross-platform alternative is used instead, to allow the library to be used in other architectures

It's used in these two instances:

https://github.com/JASory/Iridium/blob/413c32a6fb78e47357f9a51a92d6326c23e6f4af/Nuclide/src/nuclidedata/nuclidestruct.rs#L24

https://github.com/JASory/Iridium/blob/413c32a6fb78e47357f9a51a92d6326c23e6f4af/Nuclide/src/nuclidedata/decaymodes.rs#L43

[Kezii]

but also, what is the point of "simulating" the decay? why can't just the percentages be given to the user?

[JASory]

but also, what is the point of "simulating" the decay? why can't just the percentages be given to the user?

One can easily look-up the percentages so merely giving this to the user is not particularly useful. Currently the decay model is fairly simple but it at least gives some approximate energies of decay products. Obviously there are much better models that need to be implemented.

[JASory]

Thank you for the reminder to update the rand function.

[JASory]

Fixed, by resorting to XORSHIFT of the system time for platforms that don't provide RDRAND.

Additionally the branching ratio and decay probabilities can now be directly computed using x.branching_ratio<{DecayMode}>() and x.decay_probability<{DecayMode}>(time_in_seconds).