Add diverging loops to diverging function section.

I went with "associated break" here to match the terminology
given by PR #56.

Author: Havvy

src/items.md

@@ -365,9 +365,10 @@ fn my_err(s: &str) -> ! {
 ```
 
 We call such functions "diverging" because they never return a value to the
-caller. Every control path in a diverging function must end with a `panic!()` or
-a call to another diverging function on every control path. The `!` annotation
-does *not* denote a type.
+caller. Every control path in a diverging function must end with a `panic!()`,
+a loop expression without an associated break expression, or a call to another
+diverging function on every control path. The `!` annotation does *not* denote
+a type.
 
 It might be necessary to declare a diverging function because as mentioned
 previously, the typechecker checks that every control path in a function ends