cmd/bundle: include non-associated comments

https://golang.org/cl/45117 doesn't handle comments which don't
belong to any declarations. This CL addresses it.

Fixes golang/go#20627

Change-Id: I81c7cdc070efc6cb9e9f38101d7b2b8909916ba6
Reviewed-on: https://go-review.googlesource.com/45190
Reviewed-by: Alan Donovan <adonovan@google.com>
5 files changed