This patch adds a new `falloff_type` ('Inverse Coefficients') for Lamps in Blender-Internal and GLSL.

The current falloff modes use a formula like this inverse-square one:

`I = E × (D^2 / (D^2 + Q × r^2))`

While such a formula is simple for 3D-artists to use, it's algebraically cumbersome to work with. Game-designers authoring their own shaders could benefit much more by having direct control of falloff-coefficients:

`I = E × (1.0 / (coefC + coefL × r + coefQ × r^2))`

In this mode, the `distance` parameter is unused (except for 'Sphere' mode); instead relying on the designer to mathematically-model the falloff-behavior.

The UI has been patched like so: