More Rust updates:

- Some stray deriving -> derive changes
- use::{mod} -> use::{self}
- fmt.write -> fmt.write_str

This does not catch the last case of fmt.write_str in the
Show impl of a Header Item. This will need to be changed
separately.

src/header/common/mod.rs

@@ -60,13 +60,15 @@ macro_rules! bench_header(
 
 macro_rules! deref(
     ($from:ty -> $to:ty) => {
-        impl Deref<$to> for $from {
+        impl ::std::ops::Deref for $from {
+            type Target = $to;
+
             fn deref<'a>(&'a self) -> &'a $to {
                 &self.0
             }
         }
 
-        impl DerefMut<$to> for $from {
+        impl ::std::ops::DerefMut for $from {
             fn deref_mut<'a>(&'a mut self) -> &'a mut $to {
                 &mut self.0
             }