Fix libcore tests

Author: varkor

src/libcore/tests/bool.rs

@@ -1,7 +1,7 @@
 #[test]
 fn test_bool_to_option() {
-    assert_eq!(false.then(0), None);
-    assert_eq!(true.then(0), Some(0));
-    assert_eq!(false.then_with(|| 0), None);
-    assert_eq!(true.then_with(|| 0), Some(0));
+    assert_eq!(false.to_option(0), None);
+    assert_eq!(true.to_option(0), Some(0));
+    assert_eq!(false.to_option_with(|| 0), None);
+    assert_eq!(true.to_option_with(|| 0), Some(0));
 }