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

compiler/rustc_apfloat/src/lib.rs

@@ -33,6 +33,8 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/nightly-rustc/")]
 #![no_std]
 #![forbid(unsafe_code)]
+#![deny(rustc::untranslatable_diagnostic)]
+#![deny(rustc::diagnostic_outside_of_impl)]
 
 #[macro_use]
 extern crate alloc;