Block lighting fixes

- Check for luminance as well when optimizing lightmap retrieval
- Use vanilla fix for underwater lighting

src/main/java/me/jellysquid/mods/sodium/client/model/light/data/LightDataAccess.java

@@ -62,21 +62,21 @@ public abstract class LightDataAccess {
         BlockState state = world.getBlockState(pos);
 
         float ao;
+        boolean em;
 
         if (state.getLuminance() == 0) {
             ao = state.getAmbientOcclusionLightLevel(world, pos);
+            em = state.hasEmissiveLighting(world, pos);
         } else {
             ao = 1.0f;
+            em = true;
         }
 
-        // FIX: Fluids are always non-translucent despite blocking light, so we need a special check here in order to
-        // solve lighting issues underwater.
         boolean op = state.getFluidState() != EMPTY_FLUID_STATE || state.getOpacity(world, pos) == 0;
         boolean fo = state.isOpaqueFullCube(world, pos);
-        boolean em = state.hasEmissiveLighting(world, pos);
 
         // OPTIMIZE: Do not calculate lightmap data if the block is full and opaque.
-        // FIX: Calculate lightmap data for emissive blocks (currently only magma), even though they are full and opaque.
+        // FIX: Calculate lightmap data for light-emitting or emissive blocks, even though they are full and opaque.
         int lm = (fo && !em) ? 0 : WorldRenderer.getLightmapCoordinates(world, state, pos);
 
         return packAO(ao) | packLM(lm) | packOP(op) | packFO(fo) | (1L << 60);