Nano protobufs.

Like micro protobufs except:

- No setter/getter/hazzer functions.
- Has state is not available. Outputs all fields != their default.
- CodedInputStream can only take byte[] (not InputStream).
- Repeated fields are in arrays, not ArrayList or Vector.
- Unset messages/groups are null, not "defaultInstance()".
- Required fields are always serialized.

To use:

- Link libprotobuf-java-2.3.0-nano runtime.
- Use LOCAL_PROTOC_OPTIMIZE_TYPE := nano

Change-Id: I7429015b3c5f7f38b7be01eb2d4927f7a9999c80