Add macros from plugins in libsyntax_ext::register_builtins.

src/libsyntax/ext/base.rs

@@ -738,14 +738,9 @@ impl<'a> ExtCtxt<'a> {
         token::intern(st)
     }
 
-    pub fn initialize(&mut self, user_exts: Vec<NamedSyntaxExtension>, krate: &ast::Crate) {
+    pub fn initialize(&mut self, krate: &ast::Crate) {
         self.crate_root = std_inject::injected_crate_name(krate);
 
-        for (name, extension) in user_exts {
-            let ident = ast::Ident::with_empty_ctxt(name);
-            self.resolver.add_ext(ident, Rc::new(extension));
-        }
-
         let mut module = ModuleData {
             mod_path: vec![token::str_to_ident(&self.ecfg.crate_name)],
             directory: PathBuf::from(self.parse_sess.codemap().span_to_filename(krate.span)),