`s/refernces/references/`

At anal: It can make sense for unions: say, an union of `int` and `int*` could have an pointer to self or other. I won't object though, I'm *for* removing it, but it would be dishonest to not point it out.

BTW: Is the current "move" correct for unions of structs? Can we have unions of non POD? I'm not very clear on the details. In any case, its not directly related to your PR, I'm just asking the question.