This reverts commit 1549fea999.
After some further discussion with other developers in the team it becomes
clear there's no correct solution here. It is just more matter of what's
more convenient in particular case.
We're just going back to old code to avoid possible frustration with the
older files in newer blenders. This also means all HSV/HSL is considered
to be "linear" in the shading nodes.
Would be ported to 2.73 final.
These nodes were assuming sRGB input/output which is for sure wrong for the
shader pipeline which works in the linear space.
So now conversion to/from linear space happens in these nodes which makes them
making sence in the shader context but which might change look and feel of
existing scenes.
