I could apply this, but only if I get green light that this kind of
changes are ok in the current development stage as I haven't been very
involved lately. I put the patch and test programs (both for hsv_to_rgb
and rgb_to_hsv) at http://peg.it.uu.se/~sven/rgbhsv.zip if anyone's
interested. (the patch optimizes hsv_to_rgb and rgb_to_hsv to take about
95% and 60% of the times they used to take, respectively)