rustup; better comment in storage_dead_dangling test

Author: RalfJung

rust-version

@@ -1 +1 @@
-36f1f04f18b89ba4a999bcfd6584663fd6fc1c5d
+2b8fbe6b0b6db7960828bd2c9a50e52c9a5d0aef

tests/compile-fail/storage_dead_dangling.rs

@@ -18,5 +18,7 @@ fn main() {
         fill(&mut x);
         _y = x;
     }
+    // Now we use a pointer to `x` which is no longer in scope, and thus dead (even though the
+    // `main` stack frame still exists).
     evil();
 }