Derive Clone in a macro (now possible).

--HG--
extra : rebase_source : 851499a80287cb8d2271bb9d00c9844a22f8e77e

Author: chris-morgan

src/http/headers/mod.rs

@@ -883,21 +883,12 @@ macro_rules! headers_mod {
                 ExtensionHeader(~str, ~str),
             }
 
-            // Can't use #[deriving(Clone)] because of https://github.com/mozilla/rust/issues/6976
+            #[deriving(Clone)]
             pub struct HeaderCollection {
                 $($lower_ident: Option<$htype>,)*
                 extensions: TreeMap<~str, ~str>,
             }
 
-            impl Clone for HeaderCollection {
-                fn clone(&self) -> HeaderCollection {
-                    HeaderCollection {
-                        $($lower_ident: self.$lower_ident.clone(),)*
-                        extensions: self.extensions.clone(),
-                    }
-                }
-            }
-
             impl HeaderCollection {
                 pub fn new() -> HeaderCollection {
                     HeaderCollection {