Correct generated headers

```
All headers have incorrect comment, that stems form EmbeddedCGenerator.xtend 
rows 144,150 and 157:

"Serialize a Person-message ..."

Then xtend file should instead be:

"Serialize a «m.getMessageName»-message ..."
```

Original issue reported on code.google.com by `robert.b...@gmail.com` on 18 Jan 2015 at 11:23
