Clarify "smallest integer type that can contain them" to "smallest built-in integer type that can contain them"? #86
Description
I noticed today that assert_eq!(3, std::mem::size_of::<ux::u24>()); fails. I'm guessing this is covered by "The uX types take up as much space as the smallest integer type that can contain them" in the documentation, but it would be clarifying to have that read "The uX types take up as much space as the smallest built-in integer type that can contain them" (including the hyperlink).
(Separately: does there happen to be any aspiration to use as few bytes as possible for each type?)