WIP: lightmap support with >32k surface groups

[GooberRF]

This was scoped out for AF 1.3, sitting here in draft so it can be revisited later.

Current state:

• RED/D3d8/9 in game doesn't properly render lightmaps, "random" surface groups displayed as fullbright (signed short)
• RED does properly save lightmaps to the file so they can be loaded by the game
• D3d11 in game properly loads them. Works fine until geo occurs