Auto merge of #4439 - ishitatsuyuki:bench-cleanup, r=matklad
authorbors <bors@rust-lang.org>
Sun, 27 Aug 2017 07:41:33 +0000 (07:41 +0000)
committerbors <bors@rust-lang.org>
Sun, 27 Aug 2017 07:41:33 +0000 (07:41 +0000)
Gate extern crates for bench tests

I tried my best to skim through the `extern crate` statements, and I hope this will unblock the unused extern crates PR.


Trivial merge