Relax interner's Share bound

The interner uses `RefCell` internally which opted out from Share.

src/libsyntax/ast.rs

@@ -1159,14 +1159,6 @@ mod test {
 
     use std::vec_ng::Vec;
 
-    fn is_share<T: Share>() {}
-
-    // Assert that the AST remains sharable.
-    #[test]
-    fn ast_is_share() {
-        is_share::<Item>();
-    }
-
     // are ASTs encodable?
     #[test]
     fn check_asts_encodable() {

src/libsyntax/util/interner.rs

@@ -23,16 +23,13 @@
 use std::rc::Rc;
 use std::vec_ng::Vec;
 
-#[cfg(stage0)]
-use std::kinds::Share;
-
 pub struct Interner<T> {
     priv map: RefCell<HashMap<T, Name>>,
     priv vect: RefCell<Vec<T> >,
 }
 
 // when traits can extend traits, we should extend index<Name,T> to get []
-impl<T: Eq + Hash + Share + Clone + 'static> Interner<T> {
+impl<T: Eq + Hash + Clone + 'static> Interner<T> {
     pub fn new() -> Interner<T> {
         Interner {
             map: RefCell::new(HashMap::new()),