Use IdentityMap instead of CuckooObjectMap in class resolver (#877)

* Use IdentityMap instead of CuckooObjectMap in class resolver

src/com/esotericsoftware/kryo/util/CuckooObjectMap.java

@@ -32,6 +32,7 @@
  * depending on hash collisions. Load factors greater than 0.91 greatly increase the chances the map will have to rehash to the
  * next higher POT size.
  * @author Nathan Sweet */
+@Deprecated
 public class CuckooObjectMap<K, V> {
 	// primes for hash functions 2, 3, and 4
 	private static final int PRIME2 = 0xbe1f14b1;

src/com/esotericsoftware/kryo/util/DefaultClassResolver.java

@@ -37,7 +37,7 @@ public class DefaultClassResolver implements ClassResolver {
 	protected Kryo kryo;
 
 	protected final IntMap<Registration> idToRegistration = new IntMap<>();
-	protected final CuckooObjectMap<Class, Registration> classToRegistration = new CuckooObjectMap<>();
+	protected final IdentityMap<Class, Registration> classToRegistration = new IdentityMap<>();
 
 	protected IdentityObjectIntMap<Class> classToNameId;
 	protected IntMap<Class> nameIdToClass;