Don't wash out HDR vertex lite surfaces in OpenGL2

Vertex lite surfaces being brighter than light maps looks bad,
they're meant to look the same. Especially in ET, which mixes
them fequently. It's noticeable in Q3 too though.

BSP lightmaps (i.e. not external HDR lightmaps) use
R_ColorShiftLightingBytes, now *Floats (used by vertex colors)
has the same behavior.

This may be a problem for HDR lightmaps, as the RGB will always be
scaled to 0.0 to 1.0 range.

I had enabled this for non-HDR before, but now HDR needs it too.