Added dark wood and acacia wood blocks

Includes stairs, slabs, planks and saplings.

overviewer_core/src/iterate.c

@@ -260,6 +260,8 @@ is_stairs(int block) {
         case 135: /* birch wood stairs */
         case 136: /* jungle wood stairs */
         case 156: /* quartz stairs */
+        case 163: /* acacia wood stairs */
+        case 164: /* dark wood stairs */
             return 1;
     }
     return 0;