Title says it all. Formulas for Blender internal render engine, the compositor, texture, vertex and weight painting are now located in math_color_blend_inline.c. To that end the functions for floating point blending were split into a 'single channel' version, and a 'multi channel' version. Bytes blend mode were left untouched, apart from one minor correction.
Also makes the formulas to be more consistent as their implementations would slightly vary depending on where/when they were added to the code base.