Flat Protobuf hierarchy

[Sargun Dhillon]

It turns out that not all protobufs compilers support dealing with packages
correctly. The specific one I'm hitting an issue with today is gpb, the
Erlang protobuf compiler. It's also a little bit weird in Python, and some
of the other protobuf compilers. After doing a little bit of poking around,
it appears we're doing this in only one place: