Existing code in encoding/xml packages contains code which breaks
various linter rules (comments, constant and variable naming, variable
shadowing, etc).

Fixes #21578

Change-Id: Id4bd9a9be6d5728ce88fb6efe33030ef943c078c
Reviewed-on: https://go-review.googlesource.com/58210Reviewed-by: Sam Whited <sam@samwhited.com>
Reviewed-by: Ian Lance Taylor <iant@golang.org>
Run-TryBot: Sam Whited <sam@samwhited.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>