Both have the same size: 4 bytes.
So far I've just renamed print-byte to print-grapheme, but it still behaves
the same.
I'm going to support printing code-points next, but grapheme 'clusters'
spanning multiple code-points won't be supported for some time.
We now have all existing apps and prototypes going through the dependency-injected
wrapper, even though it doesn't actually implement the fake screen yet.
Slices contain `addr`s so the same rules apply to them. They can't be stored
in structs and so on. But they may be an efficient temporary while parsing.
Streams are currently a second generic type after arrays, and gradually
strengthening the case to just bite the bullet and support first-class
generics in Mu.