Update cpplint.py to google#242:

- Check indentation of public/protected/private keywords.
- Remove RTTI warning.
- Silence warning about multiple inheritance from global namespace.
- Copy ctors don't need "explicit".
- Understand "const char* const&" as a const reference.
- Remove runtime/sizeof.
- Recognize the "catch" keyword.
- List C++11 headers
- Allow sscanf()
- Allow for one extra level of nesting in template class decls.
- False positive for semicolons after single-line nameless unions.

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Review URL: https://codereview.appspot.com/15740044