librustrt: use #[deriving(Copy)]

Author: Jorge Aparicio

src/libstd/rt/unwind.rs

@@ -397,15 +397,14 @@ pub mod eabi {
     pub struct DISPATCHER_CONTEXT;
 
     #[repr(C)]
+    #[deriving(Copy)]
     pub enum EXCEPTION_DISPOSITION {
         ExceptionContinueExecution,
         ExceptionContinueSearch,
         ExceptionNestedException,
         ExceptionCollidedUnwind
     }
 
-    impl Copy for EXCEPTION_DISPOSITION {}
-
     type _Unwind_Personality_Fn =
         extern "C" fn(
             version: c_int,