RangeFull for-loop iteration fails because of IntoIterator

Saying that "[for-loop iteration] fails because .. has no IntoIterator
impl" is more direct than saying "...no Iterator impl" because for loops
sugar into IntoIterator invocations. It just happens that the other
Range* operators implement Iterator and rely on the fact that
`IntoIterator` is implemented for `T: Iterator`.

Author: matthew-piziak

src/libcore/ops.rs

@@ -1466,7 +1466,7 @@ pub trait IndexMut<Idx: ?Sized>: Index<Idx> {
 /// assert_eq!((..), std::ops::RangeFull);
 ///
 /// // for i in .. {
-/// //     println!("This errors because .. has no Iterator impl");
+/// //     println!("This errors because .. has no IntoIterator impl");
 /// // }
 ///
 /// let arr = [0, 1, 2, 3];