Patch to add resolution information to iscan

[Ross Boylan <RossBoylan@stanfordalumni.org>]

I have attached a patch so that iscan, scanning software for Epson
scanners from Epson Kowa, will record the scanning resolution when
saving .png files.  Without this, some programs (e.g., hylafax) have
to assume a resolution, and can be terribly wrong.  (I was inspired to
do this because only the lower left corner of my 400 dpi scans was
going out, since they were assumed to be postscript standard 72dpi).

I'm not sure if all versions of libpng support pHYS; if not, it might
be good to protect the code with some appropriate ifdef's.  I had
libpng10-dev (aka libpng2) as my development library when I compiled
with gcc 3.3.

Despite the name, I have used and applied the patch to iscan 1.5.2,
gcc 3.2 version.  I originally developed it against 1.5.1.

I (c) in my name and release it under GNU Public License v2 or later;
I believe this is the same license as the software it is  patching,
which is available at
http://www.epkowa.co.jp/english/linux_e/lsd_e.html.

Ross Boylan


P.S. There are some other changes I'd like to make, like having iscan
remember whether you selected png or pnm, and having it remember what
directory you are in.  I think that requires learning about gtk
preferences, though.