port-line and port-column

[Per Bothner <bothner@cygnus.com>]

A little experimentation shows that for the "first" (top) line,
port-line returns one, while for the "first" (left-most) column,
port-column returns zero.

Assuming this is intentional, it should be documented in the manual.
But I do believe that the "GNU standard" is that to be that column
numbers start with one.  I remember discussing this with Stallman,
in the context of emacs's compile.el.  Note this comment in
compile.el:
	;; Columns in error msgs are 1-origin.

Also, I noticed that before the first read-char, the port-line
is #f.  I assume this is a bug.  In any case, I suggest the
manual should say if either function can reasonably return #f
for "unknown".

(I am asking because I have similar functions in Kawa.
I have used names taken from RScheme.  I am considering
switching to the [shorter] Guile names and behavior - once that is
properly documented.)

	--Per Bothner
Cygnus Solutions     bothner@cygnus.com     http://www.cygnus.com/~bothner