Simplify by calling SliceOrd::compare

Author: Stjepan Glavina

src/libcore/slice.rs

@@ -2294,21 +2294,7 @@ impl<A> SlicePartialOrd<A> for [A]
     where A: Ord
 {
     default fn partial_compare(&self, other: &[A]) -> Option<Ordering> {
-        let l = cmp::min(self.len(), other.len());
-
-        // Slice to the loop iteration range to enable bound check
-        // elimination in the compiler
-        let lhs = &self[..l];
-        let rhs = &other[..l];
-
-        for i in 0..l {
-            match lhs[i].cmp(&rhs[i]) {
-                Ordering::Equal => (),
-                non_eq => return Some(non_eq),
-            }
-        }
-
-        self.len().partial_cmp(&other.len())
+        Some(SliceOrd::compare(self, other))
     }
 }