Comment was the only (remaining) scanned token to possibly signal a syntax error notification (and possibly launch a recovery editor in the UI) instead of producing an error token. This PR change that.

The issue was that comments are stripped from the scanner flow, but AFTER the next token is scanned (so that we can attach the comments on the token returned by next).
The proposal is if one of the comment is a bad comment (the only current case is an unterminated comment), we have to rewind the stream position (and the scanned state) just before the faulty token so that the next next will scan and return this faulty token.
The proposal is if one of the comment is a bad comment (the only current case is an unterminated comment), we just remember it, so it will be the next token (returned by next).

Note that EFFormatter have some issues with comments, so tests are let as it but will catch on future improvements.