Adjusting the Display implementation.

Display will automatically implement the to_string functionality, so the
explicit implementation was removed.

src/c_enum.rs

@@ -83,12 +83,6 @@ macro_rules! c_enum
                $($name::$variant => {stringify!($variant)})*
             }
          }
-
-         /// Get a String representation of this variant.
-         pub fn to_string(&self) -> String
-         {
-            String::from(self.to_str())
-         }
       }
 
       impl ::std::fmt::Debug for $name