Merge pull request rust-lang#36606 from brson/beta-next

Fix build error

Author: brson

src/libcore/iter/mod.rs

@@ -301,7 +301,6 @@
 
 use clone::Clone;
 use cmp;
-use default::Default;
 use fmt;
 use iter_private::TrustedRandomAccess;
 use ops::FnMut;