protoc-gen-go: follow the new code generation comment convention (#329)
protoc-gen-go: follow the new code generation comment convention (#329)

https://golang.org/s/generatedcode introduces a new convention for generated
code. To mark a file as generated, there should be a comment with no whitespace
in front of it. The comment should start with ' Code generated' and and with 'DO
NOT EDIT.', all on the same line.

fuchsia-mirror/third_party-github.com-golang-protobuf,tamird/protobuf-2,fuchsia-mirror/third_party-github.com-golang-protobuf,tamird/protobuf-2,golang/protobuf,golang/protobuf