Makes docs for references a little less confusing
Makes docs for references a little less confusing

- Make clear that the `Pointer` trait is related to formatting
- Make clear that `&T` (shared reference) implements `Send` (if `T: Send + Sync`)

graydon/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust