Adding unreleased 5.6.4 version number to Version.java

Author: ywelsch

core/src/main/java/org/elasticsearch/Version.java

@@ -98,6 +98,8 @@ public class Version implements Comparable<Version> {
     public static final Version V_5_6_2 = new Version(V_5_6_2_ID, org.apache.lucene.util.Version.LUCENE_6_6_1);
     public static final int V_5_6_3_ID = 5060399;
     public static final Version V_5_6_3 = new Version(V_5_6_3_ID, org.apache.lucene.util.Version.LUCENE_6_6_1);
+    public static final int V_5_6_4_ID = 5060499;
+    public static final Version V_5_6_4 = new Version(V_5_6_4_ID, org.apache.lucene.util.Version.LUCENE_6_6_1);
     public static final int V_6_0_0_alpha1_ID = 6000001;
     public static final Version V_6_0_0_alpha1 =
             new Version(V_6_0_0_alpha1_ID, org.apache.lucene.util.Version.LUCENE_7_0_0);
@@ -153,6 +155,8 @@ public static Version fromId(int id) {
                 return V_6_0_0_alpha2;
             case V_6_0_0_alpha1_ID:
                 return V_6_0_0_alpha1;
+            case V_5_6_4_ID:
+                return V_5_6_4;
             case V_5_6_3_ID:
                 return V_5_6_3;
             case V_5_6_2_ID: