Blender Git Loki

Fix T48663: The Soft Light blend type layer make the color darker in the
3D view

There was a misusage of the `outcol` and `texcol` params. The actual
formula should have been:

incol = facm * outcol + fact * ((one - outcol) * texcol * outcol +
outcol * scr);

To make sure the result is consistent with material mode, reuse the
material blend function (mix_soft), similarly to what most other texture
blend modes do.