Add file/lines iterator

[zevv]

That's what you get for coming up with a nice implementation. Still trying to get this into the stdlib 😄

[primo-ppcg]

I would like to reiterate my objections here.

I agree that this would be a useful additon, in particular to iterate lines of stdin as a command line tool. However, every other file/* function requires a valid file descriptor as its argument, and I don't agree that this function is special enough or important enough to be an exception.

(defn file/lines
  "Return an iterator over the lines of a file."
  [file]
  (coro
    (while (def line (file/read file :line))
      (yield line))))

I think this is a sufficient implementation.

[zevv]

@primo-ppcg I must admit you make a compelling argument there, I agree.

PR changed to drop accepting a file name.