This adds support for Canon IX-4015 scanner. The difference from other scanners
supported by this backend is that it has no highlight and shadow settings - the
corresponding bytes in set_window command must be zero or it will fail.
IX-4015 has optical resolution of 400 dpi, can interpolate up to 800 dpi (color)
or 1200 dpi (grayscale).
backend/canon.h, doc/sane-canon.man,
doc/descriptions/canon.desc: added support for FB620S and
and FS2700, by Mitsuru Okaniwa <m-okaniwa@bea.hi-ho.ne.jp>
and Ulrich Deiters <ukd@xenon.pc.Uni-Koeln.DE>
Abel