Make commandblocks compatible with all 1.8 spigot/craftbukkit versions, fix #355 (#356)

src/main/java/us/myles/ViaVersion/protocols/protocol1_9to1_8/listeners/CommandBlockListener.java

@@ -122,11 +122,15 @@ public class CommandBlockListener implements Listener {
     private long[] getPosition(Object obj) throws ClassNotFoundException, NoSuchFieldException, IllegalAccessException {
         return new long[]{
                 (long) ReflectionUtil.getSuper(obj, "a", int.class), //X
-                (long) ReflectionUtil.getSuper(obj, "c", int.class), //Y
+                (long) ReflectionUtil.getSuper(obj, isR1() ? "b" : "c", int.class), //Y
-                (long) ReflectionUtil.getSuper(obj, "d", int.class)  //Z
+                (long) ReflectionUtil.getSuper(obj, isR1() ? "c" : "d", int.class)  //Z
         };
     }
 
+    private boolean isR1() {
+        return ReflectionUtil.getVersion().equals("v1_8_R1");
+    }
+
     private CompoundTag getNBT(Object obj) throws Exception {
         ByteBuf buf = Unpooled.buffer();
         Method m = ReflectionUtil.nms("NBTCompressedStreamTools").getMethod("a", ReflectionUtil.nms("NBTTagCompound"), DataOutput.class);

src/main/java/us/myles/ViaVersion/util/ReflectionUtil.java

@@ -22,6 +22,10 @@ public class ReflectionUtil {
         return Class.forName(BASE + "." + className);
     }
 
+    public static String getVersion() {
+        return BASE.substring(BASE.lastIndexOf('.') + 1);
+    }
+
     public static Object invokeStatic(Class<?> clazz, String method) throws NoSuchMethodException, InvocationTargetException, IllegalAccessException {
         Method m = clazz.getDeclaredMethod(method);
         return m.invoke(null);