Fix meta-variable binding errors in macros

The errors are either:
- The meta-variable used in the right-hand side is not bound (or defined) in the
  left-hand side.
- The meta-variable used in the right-hand side does not repeat with the same
  kleene operator as its binder in the left-hand side. Either it does not repeat
  enough, or it uses a different operator somewhere.

This change should have no semantic impact.

src/libsyntax_ext/proc_macro_server.rs

@@ -70,7 +70,7 @@ impl FromInternal<(TreeAndJoint, &'_ ParseSess, &'_ mut Vec<Self>)>
         macro_rules! tt {
             ($ty:ident { $($field:ident $(: $value:expr)*),+ $(,)? }) => (
                 TokenTree::$ty(self::$ty {
-                    $($field $(: $value)*,)*
+                    $($field $(: $value)*,)+
                     span,
                 })
             );