nwn_gff: Write line ending without carriage return.

[Jorteck]

Resolves #42

[niv]

I did read some comment on the nim forums where cL was deprecated/replaced with \n or \p: nim-lang/Nim#7089

If I'm reading that thread correctly, then \n is the one to use - same meaning as in C now, and the indended one here (so it fits the JSON spec).

[Jorteck]

I updated the usage in nwn_gff \n. There are also some usages of \c\L in nwn_twoda, but I presume that it's always CRLF regardless of platform.

[niv]

Thanks! Yes, I agree - for 2da content, window-style newlines are the norm and that seems to work well. I'll transform it to \r\n at some point if it turns out to be a problem in future nim releases.