Improvement idea: Avoid vbLf, vbCr and even vbCrLf, use platform-specific vbNewLine instead

[ivankokan]

There are several places where vbLf, vbCr and vbCrLf are being used, e.g. https://github.com/krlmlr/Excel2LaTeX/blob/3f01291dc3cc0896f355c5e602769ef5c1cf7ac2/src/CModel.cls#L420

It would be much better to use platform-specific vbNewLine instead, and to use it consistently.

Kind regards, Ivan