Start work on dangling pointers lint

compiler/rustc_lint/src/lints.rs

@@ -1148,6 +1148,7 @@ pub(crate) struct IgnoredUnlessCrateSpecified<'a> {
 #[diag(lint_dangling_pointers_from_temporaries)]
 #[note]
 #[help]
+#[help(lint_info)]
 // FIXME: put #[primary_span] on `ptr_span` once it does not cause conflicts
 pub(crate) struct DanglingPointersFromTemporaries<'tcx> {
     pub callee: Symbol,