Reimplement Vec::push_all* with .extend

It is shorter and also fixes missed reserve call.

src/libstd/vec.rs

@@ -230,9 +230,7 @@ impl<T: Clone> Vec<T> {
     /// ```
     #[inline]
     pub fn push_all(&mut self, other: &[T]) {
-        for element in other.iter() {
-            self.push((*element).clone())
-        }
+        self.extend(other.iter().map(|e| e.clone()));
     }
 
     /// Grows the `Vec` in-place.
@@ -947,9 +945,7 @@ impl<T> Vec<T> {
     /// assert_eq!(vec, vec!(~1, ~2, ~3, ~4));
     /// ```
     pub fn push_all_move(&mut self, other: Vec<T>) {
-        for element in other.move_iter() {
-            self.push(element)
-        }
+        self.extend(other.move_iter());
     }
 
     /// Returns a mutable slice of `self` between `start` and `end`.