[R6RS] Open port I/O questions

[Michael Sperber]

Kent asked these questions:

  - add port-length and port-has-port-length? procedures?
    - and corresponding arguments to custom port makers

I very rarely use this kind of information in programs, and, when I
do, I can always call some `file-length' procedure, so I'd like to
avoid the complication.

  - allow port positions to be "magic cookies"?

Yes.

-- 
Cheers =8-} Mike
Friede, Völkerverständigung und überhaupt blabla