[Cin] Some tests on blending

[Andrea paz]

Well, we have the three main color correction plugins that clip the
final result: Histogram-Bezier, Color 3 way and the Videoscopes (I
don't know about Blue Banana and the various Contrast, Hue, etc.).
This is a big limitation. But Adam told me that Cinelerra is not made
for color correction!

Always arguing pointlessly, moreover, these are topics that have been
addressed many times in the past, I would like CinGG to be usable by
hardware not adapted with 8-bit color models, but to be fully
consistent with the RGBA-FLOAT color model (with adapted hardware).
That way they would all have a chance to use it to the fullest. But
even here Einar told me, many years ago, that it was not possible to
do it unless we rewrote almost everything from scratch, and besides,
the performance would be poor.

However, I apologize for bringing up these topics again. My initial
purpose was just wanting to retry IgorV's tutorial with Blend Algebra.