Always import all tracing macros for the entire crate instead of piecemeal by module

compiler/rustc_lint/src/lib.rs

@@ -42,6 +42,8 @@
 extern crate rustc_middle;
 #[macro_use]
 extern crate rustc_session;
+#[macro_use]
+extern crate tracing;
 
 mod array_into_iter;
 pub mod builtin;