Rollup merge of rust-lang#40142 - MajorBreakfast:patch-4, r=steveklabnik

Structs doc: Change "pointers" to "references"

Let's call them "references" instead of "pointers". That's how they're called in chapter 4.9 "References and Borrowing".

r? @steveklabnik

src/doc/book/src/structs.md

@@ -88,7 +88,7 @@ fn main() {
 }
 ```
 
-Your structure can still contain `&mut` pointers, which will let
+Your structure can still contain `&mut` references, which will let
 you do some kinds of mutation:
 
 ```rust