Replace CityHash 1.1 with xxHash as the default hash function

pom.xml

@@ -159,7 +159,7 @@
         <dependency>
             <groupId>net.openhft</groupId>
             <artifactId>zero-allocation-hashing</artifactId>
-            <version>0.2</version>
+            <version>0.4</version>
             <scope>test</scope>
         </dependency>
 

src/main/java/net/openhft/chronicle/hash/Data.java

@@ -138,7 +138,7 @@ public interface Data<V> {
      * <i>bytes</i> representation.
      */
     default int dataHashCode() {
-        return (int) hash(LongHashFunction.city_1_1());
+        return (int) hash(LongHashFunction.xx_r39());
     }
 
     /**

src/main/java/net/openhft/chronicle/hash/impl/stage/entry/InputKeyHashCode.java

@@ -29,7 +29,7 @@ public class InputKeyHashCode implements KeyHashCode {
     public long keyHash = 0;
 
     void initKeyHash() {
-        keyHash = ks.inputKey.hash(LongHashFunction.city_1_1());
+        keyHash = ks.inputKey.hash(LongHashFunction.xx_r39());
     }
 
     @Override

src/main/java/net/openhft/chronicle/hash/impl/stage/iter/IterationKeyHashCode.java

@@ -34,7 +34,7 @@ public class IterationKeyHashCode implements KeyHashCode {
     void initKeyHash() {
         long addr = s.tierBaseAddr + e.keyOffset;
         long len = e.keySize;
-        keyHash = LongHashFunction.city_1_1().hashMemory(addr, len);
+        keyHash = LongHashFunction.xx_r39().hashMemory(addr, len);
     }
 
     @Override

src/test/java/net/openhft/chronicle/map/KeySegmentDistributionTest.java

@@ -56,7 +56,7 @@ public class KeySegmentDistributionTest {
         for (int i = 0; i < size; i++) {
             random.nextBytes(keyBytes);
             String key = new String(keyBytes, StandardCharsets.US_ASCII);
-            long hash = LongHashFunction.city_1_1().hashBytes(StandardCharsets.UTF_8.encode(key));
+            long hash = LongHashFunction.xx_r39().hashBytes(StandardCharsets.UTF_8.encode(key));
             int segmentIndex = (((int) hash) & Integer.MAX_VALUE) % segments;
             // Put the segment index as a value to the map
             map.put(key, segmentIndex);