Latest version of gcc (tdm-1) 5.1.0 refuses to compile our code
on windows/386 (see issue for details). Rewrite the code.

Fixes #14328

Change-Id: I70f4f063282bd2958cd2175f3974369dd49dd8dc
Reviewed-on: https://go-review.googlesource.com/20008Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>