Handle CRLF line endings

[denismerigoux]

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The lexer (https://github.com/CatalaLang/catala/blob/master/compiler/surface/lexer.cppo.ml) is not resilient to CRLF (Windows) line endings (\r\n), basically all occurences of \n should be checked to see if they also work with \r\n.

[AltGr]

We might want to handle them anyway, but note that on Windows, conversion should happen automatically (since we use open_in and not open_in_bin) and the lexer would only see \n even if the actual file contains \r\n. So the issue here is with Windows-style files appearing in a Linux environment.