Fix several mixins for 1.16

fabric/src/main/java/com/seibel/distanthorizons/fabric/mixins/server/unsafe/MixinThreadingDetector.java

@@ -48,6 +48,9 @@ public class MixinThreadingDetector {
     }
 }
 #else
+
+import net.minecraft.server.level.ServerLevel;
+
 @Mixin(ServerLevel.class)
-    public class MixinThreadingDectector {} //FIXME: Is there some way to make this file just not be added?
+public class MixinThreadingDetector { } //FIXME: Is there some way to make this file just not be added?
 #endif

fabric/src/main/java/com/seibel/distanthorizons/fabric/wrappers/modAccessor/SodiumAccessor.java

@@ -81,11 +81,11 @@ public class SodiumAccessor implements ISodiumAccessor {
 	}
 	#else
 	@Override
-	public HashSet<DHChunkPos> getNormalRenderedChunks() {
+	public HashSet<DhChunkPos> getNormalRenderedChunks() {
 		SodiumWorldRenderer renderer = SodiumWorldRenderer.getInstance();
 		LevelAccessor height = Minecraft.getInstance().level;
 		// TODO: Maybe use a mixin to make this more efficient
-		return MC_RENDER.getMaximumRenderedChunks().stream().filter((DHChunkPos chunk) -> {
+		return MC_RENDER.getMaximumRenderedChunks().stream().filter((DhChunkPos chunk) -> {
 			FakeChunkEntity AABB = new FakeChunkEntity(chunk.getX(), chunk.getZ(), height.getMaxBuildHeight());
 			return (renderer.isEntityVisible(AABB));
 		}).collect(Collectors.toCollection(HashSet::new));

forge/src/main/java/com/seibel/distanthorizons/forge/mixins/server/unsafe/MixinThreadingDetector.java

@@ -47,6 +47,7 @@ public class MixinThreadingDetector {
 }
 
 #else
+
+import net.minecraft.world.level.chunk.ChunkGenerator;
 @Mixin(ChunkGenerator.class)
-public class MixinThreadingDectector {}
 #endif