* app/gegl/gimpoperationpointlayermode.c
(gimp_operation_point_layer_mode_process): Reuse the blending
formula from the legacy Soft light. (Actually the formula comes
from legacy Overlay but legacy Overlay and Soft light blends
pixels exactly the same.) I hereby declare the porting of the
layer modes to this GEGL operation complete. Summary:

Completely works the same:

  Normal, Dissolve, Behind, Color Erase, Erase, Anti Erase

Works the same for 100% opaque layers:

  Lighten only, Screen, Dodge, Addition, Darken only, Multiply,
  Dodge, Soft light, Hard light, Difference, Subtract, Grain
  extract, Grain merge, Divide, Hue, Saturation, Color, Value

Works different but similar:

  Overlay now uses the SVG 1.2 overlay formula which is different
  but similar to legacy Overlay

  Replace needs to be externally masked to not replace too much,
  but that is outside the scope of the layer mode porting.

svn path=/trunk/; revision=27541