System Information
Operating system and graphics card

Blender Version
Broken: 2.72
Worked: 2.71

Short description of error
We depend on access to the light energy in many of our shaders, (we used the color output of the light data node for it). This does not work any more.
For GLSL shading, the light data shader node, output "Color" exported the light color before, multiplied by the energy,
Now it only exports the color, regardless of the energy.
In the BI renderer, color is still multiplied with the energy.
The new behaviour in GLSL is more logical imho, but, the energy access is missing. Therefore I can imagine two solutions:

1. (preferred by me, but not compatible) add an energy output to the node, adapt the BI output to the new GLSL output
2. restore the old way it worked

What do you think?

Exact steps for others to reproduce the error
select the light in the scene
change the energy
compare GLSL and BI render