bump to 2.6.4 for maven

pom.xml

@@ -49,7 +49,7 @@
         <dependency>
             <groupId>org.apache.jackrabbit</groupId>
             <artifactId>jackrabbit-webdav</artifactId>
-            <version>2.6.3</version>
+            <version>2.6.4</version>
         </dependency>
 
     </dependencies>