bug#18493: 24.3.93; posn-col-row should take text-scale-mode into account

[Drew Adams]

> 1. M-x text-scale-increase (7 times)
> 2. Go to column 4.
> 3. (posn-col-row (posn-at-point))
> => (15 . 24)
> 
> Alternatively, please describe how to reliably recalculate the
> returned value in the presence of text-scale-mode.

I don't even understand why the value should change with text scale.
What part of the description of `pos-col-row' would lead one to think
that this changes with text scale?