RENDERDATA_UPDATE_COLOR was used to precompute lightEnv-dependent data
on the CPU. This is no longer done following engine upgrades, and in
particular d7d02a4740 which explictly always did this on the GPU.
ModelAbstract had a 'SetDirtyRec' hack for it because of decals, which
can also be removed. The 'dirty' bit of CRenderableObject is renderdata
for the specific item, never its props, so it never actually needs to be
recursive.
CheckLightEnv is also useless as a result, and removed.
Differential Revision: https://code.wildfiregames.com/D4453
This was SVN commit r26249.