These were introduced during C -> Go translation when the loop increment
contained multiple statements.

Change-Id: Ic8abd8dcb3308851a1f7024de00711f0f984e684
Reviewed-on: https://go-review.googlesource.com/7627Reviewed-by: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Rob Pike <r@golang.org>