libcore: add num::Int::pow() and deprecate num::pow().

Signed-off-by: NODA, Kai <nodakai@gmail.com>

src/test/bench/shootout-binarytrees.rs

@@ -93,8 +93,8 @@ fn main() {
     let long_lived_tree = bottom_up_tree(&long_lived_arena, 0, max_depth);
 
     let mut messages = range_step(min_depth, max_depth + 1, 2).map(|depth| {
-            use std::num::pow;
-            let iterations = pow(2i, (max_depth - depth + min_depth) as uint);
+            use std::num::Int;
+            let iterations = 2i.pow((max_depth - depth + min_depth) as uint);
             Future::spawn(proc() {
                 let mut chk = 0;
                 for i in range(1, iterations + 1) {

src/test/compile-fail/lint-dead-code-4.rs

@@ -14,7 +14,7 @@
 
 extern crate libc;
 
-use std::num;
+use std::num::Int;
 
 struct Foo {
     x: uint,
@@ -23,7 +23,7 @@ struct Foo {
 }
 
 fn field_read(f: Foo) -> uint {
-    num::pow(f.x, 2)
+    f.x.pow(2)
 }
 
 enum XYZ {