This code is dead as a result of

* removing the Follow pass
* moving rotation detection from walk to ssa

Change-Id: I14599c85bedb4e3148347b547e724187920182c4
Reviewed-on: https://go-review.googlesource.com/36484
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>