fix stringify docs

Author: durka

src/libcore/macros.rs

@@ -682,15 +682,15 @@ mod builtin {
     #[cfg(dox)]
     macro_rules! file { () => ({ /* compiler built-in */ }) }
 
-    /// A macro which stringifies its argument.
+    /// A macro which stringifies its arguments.
     ///
     /// For more information, see the documentation for [`std::stringify!`].
     ///
     /// [`std::stringify!`]: ../std/macro.stringify.html
     #[stable(feature = "rust1", since = "1.0.0")]
     #[macro_export]
     #[cfg(dox)]
-    macro_rules! stringify { ($t:tt) => ({ /* compiler built-in */ }) }
+    macro_rules! stringify { ($($t:tt)*) => ({ /* compiler built-in */ }) }
 
     /// Includes a utf8-encoded file as a string.
     ///