Arity-based parameter overloading

A better proposal to have better names of functions in the standard lib.
It's really unclear how this would work, since `ToStr` and `ToStrRadix` are completely separate traits, and most of the things that implement `ToStr` have no concept of "radix".

I also don't see any subjective benefit to giving these functions the same name. Right now if you look in the documentation for numeric types you will see implementations of the `ToStrRadix` type (as well as `ToStr` for any which do this "default base 10" thing, though a quick glance through did not find any examples). You can click on the `ToStrRadix` trait to get documentation for what `to_str_radix` does and on `ToStr` to get documentation for .what `to_str` does. I don't see how you can sensibly merge this documentation, so your function merging is only skin deep, so to speak.