Add diagnostic translation lints to crates that don't emit them

compiler/rustc_span/src/lib.rs

@@ -20,6 +20,8 @@
 #![feature(negative_impls)]
 #![feature(min_specialization)]
 #![feature(rustc_attrs)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 #[macro_use]
 extern crate rustc_macros;