Added a format option to inhibit output of .Note field in
printing, and enabled that option during export.
Added test.

Fixes #13777.

Change-Id: I739f9785eb040f2fecbeb96d5a9ceb8c1ca0f772
Reviewed-on: https://go-review.googlesource.com/18217Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: David Chase <drchase@google.com>