Make debug message about resolving extern crate statements more helpful

Author: bkoropoff

src/librustc/metadata/creader.rs

@@ -145,7 +145,7 @@ fn extract_crate_info(e: &Env, i: &ast::ViewItem) -> Option<CrateInfo> {
     match i.node {
         ast::ViewItemExternCrate(ident, ref path_opt, id) => {
             let ident = token::get_ident(ident);
-            debug!("resolving extern crate stmt. ident: {:?} path_opt: {:?}",
+            debug!("resolving extern crate stmt. ident: {} path_opt: {}",
                    ident, path_opt);
             let name = match *path_opt {
                 Some((ref path_str, _)) => {