protobuf-c-text couldn't parse text generated by go's proto.MarshalTextString

for proto message like

```
message Foo {
  string s = 1
}

message Bar {
  Foo foo = 1
}
```

go's proto.MarshalTextString will marshal proto to text as

```
foo: <
  s: "test"
>
```

but protoc-c-text failed to parse the text file
```
 Expected a '{', got a ':' - 'foo' is a message type field.
```


