tokenize_file() now returns a single list of TokenizedLine structs,
carrying the same information as before.  We were otherwise going to grow a
fourth list to deal with error messages, and that was getting a bit silly.

Haribabu Kommi, revised a bit by me

Discussion: https://postgr.es/m/CAJrrPGfbgbKsjYp=bgZXhMcgxoaGSoBb9fyjrDoOW_YymXv1Kw@mail.gmail.com