fix pylintrc to run with pylint/python 3

Current pylintrc will cause an error in pylint, if invoked with python 3:

```
configparser.DuplicateSectionError: While reading from '/home/felix/projects/boto/pylintrc' [line 304]: section 'MESSAGES CONTROL' already exists
```

Merging the section solves this easily.
Hmm, so you mean assign the value twice will merge the options?