Lookup table and float to int conversion and performance

[LukasT.dev@gmail.com]

> ...
> [1] http://bitbucket.org/cyrille/lut
> [2] http://www.mega-nerd.com/FPcast/
> [3] http://www.gimpusers.com/forums/gegl-developer/227-speeding-up-GEGL-
> operations-in-GIMP.html
> [4] http://mysite.verizon.net/spitzak/conversion/sketches_0265.pdf

Very interesting stuff. I found at [3] link to [5] about converting floats into 
8-bit RGB for screen or monitor. Do we do that properly?

[5] http://mysite.verizon.net/spitzak/conversion/sketches_0265.pdf